题目

生物体结构和功能的基本单位是（ ） A . 个体 B . 种群 C . 细胞 D . 生物圈 答案：C 此题要求改正所给短文中的错误。对标有题号的每一行作出判断：如无错误，在该行右边横线上画一个勾(√)；如有错误(每行只有一个错误)，则按下列情况改正：     此行多一个词：把多余的词用斜线(＼)划掉，在该行右边横线上写出该词，并也用斜线划掉。     此行缺一个词：在缺词处加一个漏字符号(∧)，在该行右边横线上写出该加的词。     此行错一个词：在错的词下划一横线，在该行右边横线上写出改正后的词。     注意：原行没有错的不要改。     It is one thing to land science instruments on Mars; however, it is quite    76._______ another to establish a base for humans to explore planet. Daytime temperatures   77._______ can be rise above freezing, but, because of the extremely thin atmosphere,       78._______ the sun heat radiates back into space. Even at the equator, the temperature      79._______ drops—50℃at night. In fact, there is no ozone(臭氧) layer to keep out          80._______ ultraviolet(紫外线的)radiation, and hardly some oxygen for either breathing   81._______ and burning conventional fuels. But despite all these problems, scientists are    82._______ currently working transport and clothing for Mars and an artificial environment    83._______ in which colonists could live. However, the potential cost make the idea of       84._______ human life on Mars nothing other than a fantastic dream.                     85._______