单选题 Eating in space is different from eating on the earth. The food that astronauts (宇航员) carry with them does not look like the food we eat.
Some food is carried in closed bags. It is cooked and frozen (使结冰，冻结) before the astronauts get it. All the water is removed (去掉) from the food. In the space capsule (座舱), the astronaut puts the water back. He "shoots" hot or cold (寒冷的,伤风) water into the food bag with a special gun (枪,炮). He eats the food through a small hole in the bag.
Other foods come in bite (咬,刺骨) sizes. The astronaut puts a whole (全部,完整的) piece in his month at once. There can be no crumbs (碎屑). Crumbs would float (飘浮,浮游物) around the capsule (胶囊,小盒) and get in the way. Meat, cake, and cereal (谷类食物) often come in bite-sized pieces.
Astronauts cannot drink water from open cups. The water would float in drops in the air. The water is put in the special gun. The astronaut shoots the water into his mouth.
Eating in space is not easy. Astronauts must learn to eat this way.

单选题 Why can't astronauts drink water from cups?

单选题 The opposite (对面的，对立物) of the word sink (沉淀) in the story (故事，新闻报道) is ______.

单选题 From the story, we can conclude (得出结论) ______.

单选题 The main (主要的，总管道) idea of the whole story is that ______.

单选题 The story wants to tell us that ______.