1.spend “花费”，其主语通常为人，既可指花费时间，也可花费金钱，结构为：
[sb + spend + some time/money on sth 某人花费时间/金钱做某事。
sb. + spend + time/money (in) doing sth
Every student spends two hours (in) doing his homework every day.
每个学生每天花两小时做作业。
=Every student spends two hours on his homework every day
Tom spent ten dollars (in)buying the shoes. 汤姆花了10美元买这双鞋。
2. take “花费”，其主语通常是形式主语
It took him two hours to finish the exercises.
These things will take me two weeks.
3. cost 指花费，主语通常为某物
The book cost me 30 yuan.
It costs a lot to buy a house.
4. I will pay for your dinner.
I paid the shopkeeoer $200.
