—Who sings best in your class? —Mary _____.
I hate when people talk with their mouths full.
--- Aren’t you ____ that Wang Kai got full marks in the English examination? ---- Yes, it is really _______.
She brought with her three friends, none of I had ever met before.
We wonder ___________ quite a number of living things are dying out.
He was so busy that he couldn’t help ____________ the experiment.