Fruit and vegetables are good for us. We need them healthy.A. keepB. keeping C. to keep

问题补充：

Fruit and vegetables are good for us. We need them healthy.

A. keep

B. keeping

C. to keep

D. keeps

答案：

A. keep

B. keeping

(答案→)C. to keep

D. keeps

解析：句意:水果和蔬菜都对我们是有益的，我们需要它们来保持健康。这里的谓语动词need，动词不定式来作目的状语，根据句意故选C。