Question

【题目】It is known that it's the soldiers' first job ________ (guard)our country.

Answer 1

【答案】to guard

【解析】

句意：众所周知，保卫国家是战士们的首要工作。

根据句子结构可知，此句是主语从句，it是从句的形式主语，此空是真正的主语，要用动词不定式，故答案为to guard。