_____chapter in Oxford English often consists of four parts．—That’s right．And this chapter mainly talks about _____environmental problems．

I’ll never forget the days ______ we spent together.

When I am walking in the street,I________some ads every time. —So am I.I hate it.It’s a waste of paper.

I took the wrong train ______, I didn’t even know it until half an hour later. [ ]

Many students don’t know how to ______ stress(压力).