《2025年轻松总复习暑假作业七年级英语》

D
What will astronauts eat when a space trip takes years?
"Lots of fresh vegetables," says Dr Janet Williams. Her team spent years learning how to grow plants in a space station.

As usual, seed seedlings astronaut George White looked into the closed plant room and found the problem. The stems weren't growing upward and the roots weren't growing downward. On Earth, gravity(重力) helps a plant's stems and roots to find "up" and "down". However, in the space station, there was almost no gravity.
Dr Williams gave a piece of advice: give the plants more light, because plants also use sunlight to find their way. And it worked. When the plants had more light, the stems turned up and the roots went down.
Now Dr Williams worried about the next problem: Would her baby plants live to flower?
Many plants died in the space station, because the space plants were hungry for air. Plants live by taking in $CO_2$ from the air. When a plant uses it up in the air around, the plant needs moving air to bring more $CO_2$. On Earth, the air is always moving. And with these air movements, plants get enough $CO_2$.
Dr Williams tried a new greenhouse with a fan to keep the air move. The plants loved it. They flowered and even produced(产生) more seeds.
"And this," says Dr Williams, "is good news for long-term space travel."
()1. Why did Dr Williams's team try to grow plants in space?
A. To produce fresh air for astronauts.
B. To help astronauts relax a lot.
C. To give food for space trips.
D. To make the space garden more beautiful.
()2. How did light help work out the problem in Paragraph 3?
A. It caused the gravity to change.
B. It encouraged the plants to grow faster.
C. It helped the plants to grow in the right direction.
D. It showed the astronauts where to plant vegetables
()3. Why did many plants die in the space station?
A. The light was too strong.
$B. There was too much CO_2.$
C. There was not enough room to grow.
D. The air condition(条件) was not good enough.

答案： D) 1. C 2. C 3. D