．The fact has worried many scientists the earth is becoming warmer and warmer these years

问题补充：

．The fact has worried many scientists the earth is becoming warmer and warmer these years.

A. what

B. which

C. that

D. though

答案：

A. what

B. which

(答案→)C. that

D. though

解析：考查同位语从句。句意；地球这些年以来正在变得越来越暖和，这个事实已经使很多科学家忧心忡忡。主句是The fact has worried many scientists，而后面的从句为同位语从句，修饰主句主语the fact，补充解释它（即该事实）的具体内容。从句中不缺少句子成分，故引导词用that。选C。