Air or is called the atmosphere surrounds the whole world.A. whatB. whichC. thatD. i

问题补充：

Air, or is called the atmosphere, surrounds the whole world.

A. what

B. which

C. that

D. it

答案：

(答案→)A. what

B. which

C. that

D. it

解析：此题考查名词性从句。由题意“空气，或称之为大气，环绕着整个地球”可知or is called the atmosphere是作air的同位语，且同位语是一句子，缺少主语，因此要用what，what=the thing which(that)。that在引导名词性从句时在从句中不作任何句子成分。