People should think about they can have a positive influence on the planet.A. whyB. thatC

问题补充：

People should think about they can have a positive influence on the planet.

A. why

B. that

C. what

D. how

答案：

A. why

B. that

C. what

(答案→)D. how

解析：考查宾语从句。 宾语从句How they can have a positive influence on the planet作为think about的宾语。本句主要是从句意出发。句意：人们应该考虑他们怎么样才能对地球有积极的影响。