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

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. whose

答案：

A. what

B. which

(答案→)C. that

D. whose

解析：句意：这些年地球变得越来越暖这个事实困扰着许多科学家们。这里是同位语从句，先行词是fact，同位语从句中不缺少成分，that在从句中不做成分，故选C。