Question

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

1. A.
   what
2. B.
   which
3. C.
   that
4. D.
   it

Answer 1

A
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。