John must have forgotten to return the magazine to the library yesterday, _________?

we have done a lot to build a low-carbon economy,yet it is still _________ ideal. We have to work even harder.

Do you have a pen —No, I _______.

Many wild animals are , and it’s time for us to do whatever we can to protect them.

The most satisfying life is one ______ you know thethings you’re interested in and pursue it in your own way