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 distance problem.
(2) spend time ／ money (in) doing sth. 花费时间（金钱）做某事。
例：They spent three years (in) getting into university.
(3)spend money for sth. 花钱买……。
例：His money was spent for car.
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 refrigerator costs a lot of money.
(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.
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 get into university.
(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.
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.
(2)pay for sth. 付……的钱。
例：I have to pay for the book lost.
(3)pay for sb. 替某人付钱。
例：Don't worry!I'll pay for you.
(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.
（6）pay off one's money还清钱。
例：I have paid off your money.
spend/cost/pay/take
(1)spend的主语通常是人，往往用于以下句型：
（sb）spend some money/some time on sth.
(sb)spend some money/some time(in)doing sth.
例如： I spent fifty yuan on the coat.
= I spent fifty yuan (in) buying the coat. 我花50元买了这件大衣。
He spent three days on the work.
= He spend three days (in) doing the work. 我干这项工作用了3天。
(2)take常用于“占用、花费”时间，其主语通常为形式主语“it”或物。句式是：
It takes/took sb.some time to do sth＝Sth.takes sb.some time.
例如： It took me three years to draw the beautiful horses.
画这些漂亮的马花费了我3年时间。
The work will take me two days.这项工作花了2天时间。
(3) pay为“付款、赔偿”之意，主语通常是人，往往是sb. pays some money for sth或pay sb.(some money for sth)
例如： I paid fifty yuan for the coat.我花50元买了这件大衣。
He has paid the doctor 50 pounds for the medicine? 他买药已付医生50英镑。
How much did you pay him? 你付他多少钱？
(4) cost的主语必须是某物。spend … on sth．/in doing sth．的主语必须是人。pay … for 的主语也是人。It takes sb． 时间（或钱）to do sth．的主语则必须是形式主语It。 动词cost的常用用法是sth.cost (sb.) some money。
