Question

it's very important for us to be in a good mood

it is very important for us to be in a good mood中为何用to be.it指代什么?

Answer 1

it is + 形容词+不定式（to do / be) 固定句型
for sb 表示动作发出者
句子主语是不定式的句子,而把形式主语it提到句子最前
所以it 指代to be in a good mood