—_____chapter in Oxford English often consists of four parts.—That’s right.And this chapter mainly talks about _____environmental problems.
---__________? ---He is tall and strong.
Which floor do you live ______ this building?
The post office is about five kilometers ______ our school.
The maths problems are too hard, only ______ people can work them out.
---______ does he go to Guangzhou on business? ---Three or four times a year.