spend on 和spend in 到底用哪一个?

spend on 和spend in 到底用哪一个?
spend on 和spend in 到底用哪一个?

spend on 和spend in 到底用哪一个?
两种都有：
spend +钱、时间+ on sth（名词）
spend + 钱、时间+in doing sth (IN 可省,动词ING形式）
如
I spent ten yuan on the book.
I spent ten yuan（ in） buying the book.

spend .. on + sth.
spend.. ( in) doing sth.
如： I usually spend an hour on my homework every day.
= I usually spend an hour in doing my homework every day.

spend .. on + sth.
spend .. on + sth.
spend.. ( in) doing sth.