I want to be a volunteer some day. I feel is my duty to help others.A. thisB. thatC. them

问题补充：

I want to be a volunteer some day. I feel is my duty to help others.

A. this

B. that

C. them

D. it

答案：

A. this

B. that

C. them

(答案→)D. it

解析：考查it做形式主语。It是形式主语，真正的主语是不定式to help others.句意：我想有一天我也去做志愿者。我感觉到帮助别人是我们的职责。根据句意说明D正确。