—_____?    —Sorry, I can’t.

Since it will take years to know the effect of genetically modified food, it’s more sensible to give it a second thought before we eat it,        it?

Many of your classmates dislike having to stay up late doing their lessons, _____? 

Are those your pen friends?    Yes,              .

I don’t believe you can do today’s job with yesterday’s methods and be in business tomorrow，                                                   ?