spend in（on）的用法?

很少见 spend time in doing sth 这种说法.
一般而言,spend time 后如果直接跟“动名词”（v+ing）,既不用 in 也不用 on.
如果后面跟的是地点状语,用 in；如果跟的是事或人,用 on.例：
My parents spent their vacation in Paris.
I spent all my resources on futile projects.
John spent most of his time on his girlfriend.

当作花费时间或金钱时,后面接on后用名词

spend的主语必须是人,常用于以下结构：
(1) spend time ／money on sth. 在……上花费时间(金钱).例：
I spent two hours on this maths problem. 这道数学题花了我两个小时.
(2) spend time ／ money (in) doing sth. 花费时间(金钱)做某事.例：
They spent two years (in) building this bridge. 造这座桥花了他们两年时间.
(3)spend money for sth. 花钱买…….例：
His money was spent for books. 他的钱用来买书了.
cost的主语是物或某种活动,还可以表示"值",常见用法如下：
(1)sth. costs (sb.) ＋金钱,某物花了(某人)多少钱.例：
A new computer costs a lot of money. 买一台新电脑要花一大笔钱.
(2) (doing) sth. costs (sb.) ＋时间,某物(做某事)花了(某人)多少时间.例：
Remembering these new words cost him a lot of time. 他花了大量时间才记住了这些单词.
注意：cost的过去式及过去分词都是cost,并且不能用于被动句.
take后面常跟双宾语,常见用法有以下几种：
(1)It takes sb. ＋时间＋to do sth. 做某事花了某人多少时间.例：
It took them three years to build this road. 他们用了三年时间修完了这条路.
(2)doing sth. takes sb. ＋时间,做某事花了某人多少时间.例：
Repairing this car took him the whole afternoon. 他花了一下午修车.
pay的基本用法是：
(1) pay (sb.) money for sth. 付钱(给某人)买…….例：I have to pay them 20 pounds for this room each month. 我每个月要付20英磅的房租.
(2)pay for sth. 付……的钱.例：
I have to pay for the book lost. 我不得不赔丢失的书款.
(3)pay for sb. 替某人付钱.例：
Don’t worry! I'll pay for you. 别担心,我会给你付钱的.
(4)pay sb. 付钱给某人.例:
They pay us every month.他们每月给我们报酬.
(5)pay money back 还钱.例：
May I borrow 12 yuan from you? I'll pay it back next week. 你能借给我12块钱吗?下周还你.
(6)pay off one's money还清钱.