He felt to remind the public to protect the environment.
A. his duty
B. that is his duty
C. it his duty
D. it is his duty
网友回答
A. his duty
B. that is his duty
(答案→)C. it his duty
D. it is his duty
解析：此题考查it作形式宾语，真正的宾语是后面的不定式，作形式宾语的结构为 feel/ make/find等等 + it + 名词或形容词+ to do /that 从句，句意：他感到提醒公众保护环境是他的职责。所以选C。