--Didn’t your brother ___ go to school by bike? ---Yes, he did. But he __ walking to school now.
My friend and I joined a program ______ Green China.
Bad luck! My watch is broken, ____ it doesn’t _____.
—Beijing has improve a lot these years. —_____ and_____.
_____ we have built “the Green Wall’, _____we still need to work hard to protect our environment.
— Tony, may I have a talk with you now? — Sure. Oh, it’s noisy here. Let’s go ______.