选词填空，用所给动词的适当形式填空。

celebrate,  happen,  peel,  discuss,  improve

What _____________________ if people don’t have any phones or computers?
He cut the tomato into four pieces without ____________ it.
It’s impossible for the students ________________ their grades without hard work.
Don’t talk loudly. They ________________________ something important.
The Greens always ______________________ Thanksgiving Day in the restaurant.