He feltto work for human rights and progress.A. it his dutyB. his dutyC. that is a duty D.

问题补充：

He feltto work for human rights and progress.

A. it his duty

B. his duty

C. that is a duty

D. that is his duty

答案：

(答案→)A. it his duty

B. his duty

C. that is a duty

D. that is his duty

解析：此处 it作形式宾语。