Version D — Grade 4 ELA Practice Test

Every Saturday morning, Ada went with her father to the repair shop. Not her father's shop — her father was a dentist — but the shop of a man named Mr. Olusegun, who fixed radios, clocks, and small appliances out of a narrow storefront on the corner of Ash and Fifth.

Ada was allowed to watch but not touch. She sat on a stool and watched Mr. Olusegun take things apart and put them back together. He worked slowly and talked while he worked — not to Ada exactly, but in a general way, as if he was thinking out loud.

"Everything broken has a reason," he said one Saturday, peering at a clock through a magnifying glass. "The reason is always simple. The clock is complicated; the reason it stops is usually not."

Ada's father brought a toaster that had started making a burning smell. Mr. Olusegun opened it up, found a crumb trap that had filled completely, cleaned it in thirty seconds, and handed it back.

"That's all?" Ada's father said.

"Usually is," Mr. Olusegun said.

On the way home, Ada's father asked her what she had learned.

"That the problem is simple," Ada said. "But you have to know enough to look in the right place."

Her father nodded. "That's what most things are about," he said.

Ada thought about that for a long time afterward. Not just about clocks and toasters — about everything that seemed complicated from the outside.

Every year, billions of animals make extraordinary journeys. Arctic terns fly from the Arctic to the Antarctic and back — a round trip of roughly 70,000 kilometers. Monarch butterflies travel up to 4,800 kilometers from Canada to central Mexico. Humpback whales cross entire ocean basins. These journeys, called migrations, are among the most remarkable phenomena in the natural world.

What guides migrating animals? Scientists have found that different species use different navigational tools, and many use several at once.

Many birds use the sun as a compass, adjusting for the sun's position as it moves across the sky throughout the day. At night, some species navigate by the stars — young birds appear to be born with the ability to identify the axis of the night sky and use it for orientation.

Earth's magnetic field also plays a role. Many species — including birds, sea turtles, and salmon — have magnetite crystals in their tissues that may allow them to sense magnetic fields and use them like a GPS. Sea turtles, for example, navigate across thousands of kilometers of open ocean and return to the exact beach where they hatched to lay their own eggs.

Smell and memory also contribute. Salmon use smell to identify and return to the specific stream where they were born. Gray whales follow coastlines, possibly using memory and landmarks as guides.

Scientists continue to discover new mechanisms. What seems clear is that animal navigation is not a single system but a flexible, redundant set of abilities — one that has evolved over millions of years to be robust enough to guide animals home across distances humans are only beginning to appreciate.

Grandma Rose had never sent an email in her life, and at eighty-two, she had no intention of starting. She wrote letters — real ones, on cream-colored paper — in a handwriting so small and even that Jonelle sometimes needed her mother's reading glasses to make it out.

Every month, a letter arrived. Jonelle wrote back. Not always promptly. Sometimes not for three weeks. But she wrote.

The letters were about ordinary things: the neighbor's new dog, a recipe that hadn't worked, a dream Grandma Rose had about a beach she visited sixty years ago. Jonelle wrote about school, about the kids on her soccer team, about a movie she had seen twice because the first time she hadn't understood the ending.

One month the letter came with a clipping from a local newspaper — an obituary for someone Jonelle had never heard of. Grandma Rose had written in the margin: He taught me to read. I was eight. He was eighty-nine.

Jonelle looked at the clipping for a long time. She had never thought about a time when Grandma Rose didn't know how to read. It made her grandmother seem both more distant and more real at the same time.

She wrote back that night, for the first time asking a question she had never asked before: What was it like when you learned?

Grandma Rose's response came two weeks later. It was six pages long. It was the best letter Jonelle had ever received.

When a pathogen — a disease-causing organism such as a virus or bacterium — enters the body, the immune system responds. White blood cells identify the pathogen, and the body begins producing proteins called antibodies, which are specifically shaped to attach to and neutralize that pathogen. This process takes time, during which the person may become very ill.

The key to this system is memory. Once the immune system has encountered a pathogen and made antibodies for it, it retains a population of memory cells. If that pathogen enters the body again, the response is faster and more powerful — often too fast for the pathogen to cause illness.

Vaccines work by training this memory system without requiring the person to become sick first. A vaccine introduces something the immune system can recognize — either a weakened or inactivated form of the pathogen, a fragment of it, or (in newer types) genetic instructions that tell the body's own cells to produce a recognizable fragment. The immune system responds, makes antibodies, and most importantly, creates memory cells.

When the person later encounters the real pathogen, the immune system responds quickly because it has already prepared. The protection this creates is called immunity.

Vaccines do not just protect the person who receives them. In a community where most people are immune, a pathogen has fewer opportunities to spread, which protects people who cannot be vaccinated — such as newborns or people with certain medical conditions. This is called herd immunity or community protection.

The development of vaccines has eliminated or dramatically reduced diseases that once killed or disabled millions of people each year, including smallpox, polio, and measles.

The hardest part of the relay, Imani had decided, was not the running. It was the handoff.

She had practiced it a hundred times. Stand in the exchange zone. Start moving at the right moment. Extend your arm back without looking. Feel the baton, grip, go. Thirty meters of coordinated motion between two people — and if one of them flinched or hesitated, the baton would clatter to the track and twenty seconds of running would be gone.

Her partner in the handoff was a girl named Priya who had the fastest hundred meters on the team. Imani's job was the second leg — she received the baton from Priya and passed it to the anchor. She was not the fastest runner. She was the most reliable.

Coach called it "the quiet position." "Every relay has one," she said. "It's the leg nobody talks about. It's also the one that keeps everything together."

At the regional meet, Priya came off the first curve at full speed. Imani felt the baton in her hand before she saw it — the weight, the texture, the certainty of it — and she ran.

At the exchange with the anchor, the handoff was clean. The anchor ran the last leg and they finished second.

After, Priya found Imani.

"That was a perfect handoff," Priya said.

Imani looked at her. "Both of them," she said.

Priya blinked, then smiled. "Both of them."

They had done it together. That was the whole thing.

The ocean covers more than 70 percent of Earth's surface, yet more than 80 percent of it remains unexplored. The deep ocean — below about 200 meters — is a world of near-total darkness, crushing pressure, and temperatures just above freezing. For most of human history, it was entirely inaccessible.

Light disappears rapidly underwater. In the euphotic zone (0–200 meters), photosynthesis is possible; this is where most ocean life familiar to us exists. Below the euphotic zone, there is no sunlight. The midwater zone (200–1,000 meters) receives only faint traces of light. Below 1,000 meters, in the bathypelagic zone, there is complete darkness.

Yet life exists throughout. The deep sea contains some of the most unusual organisms on Earth. Anglerfish use bioluminescent lures to attract prey in total darkness. Vampire squid can invert their cloaks to avoid predators. Giant tube worms live near hydrothermal vents — cracks in the ocean floor where superheated water and chemicals emerge — and survive not on photosynthesis but on chemosynthesis, using chemical energy from the vents.

Hydrothermal vents were discovered in 1977 and revolutionized biology: they proved that life does not require sunlight. The organisms there exist in a complete ecosystem built on chemical energy — a discovery that has changed how scientists think about where life might exist elsewhere in the universe.

Exploring the deep ocean requires specialized submersibles that can withstand pressures many times greater than at sea level. Only a handful of humans have descended to the deepest points. Scientists estimate that millions of species in the deep ocean remain undiscovered.

Ms. Petrov told her eighth-grade English class on the first day that they would write a letter each week to someone they admired.

"Not to send," she said. "To write."

Nico thought this was a strange assignment. A letter you didn't send was just talking to yourself.

For the first week he wrote to a basketball player. For the second, a musician. By the fourth week, without entirely meaning to, he wrote to his older brother who had left for college and hadn't called home much.

He didn't say anything angry in the letter. He said he missed the way his brother used to watch movies with him on Friday nights and how the apartment felt quieter now and how sometimes he started a sentence to say something to his brother and then remembered his brother wasn't there to hear it.

He reread it. He hadn't known he was going to say any of that.

The next day, he called his brother. He didn't read the letter. He didn't need to. He said some of the same things differently, out loud, and his brother was quiet for a moment and then said he missed Friday nights too and that he should call more.

After the call, Nico thought about what the letter had done. It hadn't been sent. It hadn't needed to be. The act of writing it had shown him what he hadn't known he felt.

He went back to class the next week with a different understanding of what Ms. Petrov had meant.