Space vegetables are grown from seeds（种子）. They have been taken to and brought back from outer space. The seeds are influenced by the radiation（辐射）and low gravity（重力）in outer space. When they are brought back to the earth, these seeds produce vegetables that are bigger, healthier and more nutritious（有营养的）than normal vegetables. People needn't worry, because space vegetables are actually very healthy.
Here are some facts that you should know about space vegetables:
Space vegetables are grown from seeds (A) ______ are carefully chosen. After seeds are brought back from space, (C) ______ they are tested to make sure that the vegetables they grow will be safe to eat. There are no traces（痕迹）of radiation after testing.
Space vegetables are better for you than normal vegetables. (B) ______ example, space tomatoes stay fresh for twenty days, which is one week longer than normal tomatoes.
After genetically modified（转基因）food came into the market, people worried that they were eating unknown things. Unlike genetically modified food, space vegetables have not been genetically changed. This means that no new genes（基因）are put into the vegetables. (D) So they won't be bad for your health.
【小题】在文中（A）和（B）的空白处分别填入适当的词： ______ ______
【小题】文中划线部分（C）指代的是： ______

【小题】将文中划线部分（D）改写为：So they won't ______ ______ to your health.

【小题】从文中找出两个能说明太空蔬菜特点的形容词： ______ ______

【小题】从文中找出能说明本文中心大意的单词或者短语： ______