let's think it 还是let's think about it 为什么

let's think it 还是let's think about it 为什么
let's think it 还是let's think about it 为什么

let's think it 还是let's think about it 为什么
think about it.

第二个
think不及物动词，要加一个介词，所以是think about it

let's think about it, think about 固定搭配，考虑