spend 后既可接時間又可接錢,如：
I spend two hours on my homework．或 I spend two hours
in doing homework．
I spend 100 dollars on the coat．
cost后只能接錢,如：
It costs me much money to buy the books.
take 后只接時間,如：
It takes her 3 hours to finish her homework.
注意cost 和 take 不能用人做主語．
plenty of后只接不可數(shù)名詞,a lot of后既接可數(shù)又能接不可數(shù)名詞．