Whose job it is to advise 有錯嗎?

The executive branch includes the President, the Vice President, and all of the departments, such as the Department of State. Each department head has the title of Secretary, such as the Secretary of Defense. All of the secretaries together form the Cabinet, whose job it is to advise the... show more The executive branch includes the President, the Vice President,
and all of the departments, such as the Department of State.
Each department head has the title of Secretary,
such as the Secretary of Defense.
All of the secretaries together form the Cabinet,
whose job it is to advise the President.

以上文章裡
"whose job it is to advise the President."
it 是否是多餘甚至是錯的?
為何不說成
"whose job is to advise the President."

是否可從文法角度分析,越詳細越好,多謝.
4 answers 4