There is no doubt the earth is becoming warmer.A. whetherB. thatC. ifD. why

问题补充：

There is no doubt the earth is becoming warmer.

A. whether

B. that

C. if

D. why

答案：

A. whether

(答案→)B. that

C. if

D. why

解析：考查doubt的句型，该处为固定句型，there is no doubt that..意为毫无疑问、当doubt用于疑问句和否定句中，doubt后面要用that，用于肯定句中后面要用whether 或者if。