CCTV-10 often plays _____ around the world . It can help us learn more about not only nature but also different cultures and customs.

We are confident that the step the Chinese government has taken to cope with the current crisis is ______ of great significance.

—Can I help you?—I’d like to buy a present for my father’s birthday,       at a proper price,but of good use.

I have enough drinking water but ________ to waste.

Peter is my best friend. He often helps ______ with science.