include---- four books are included in the bag-------除了书,还有其他东西
contain----four books are contained in the bag.-----包里面只有4本书,没有其他东西
cover------1 include----her lecture covers the subject thoroughly
2 == be enough for ---------will 500 yuan cover your one-day trip to Suzhou?
3 cover a distance of 200 kilometers === travel ----- we covered 150 kilometrs northward yesterday