Air, or is called the atmosphere, surrounds the whole world.
A. what
B. which
C. that
D. it
网友回答
(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。