Some steps have been taken to prevent the forest ____ .

How about your last weekend?—- It was boringI______ anything

What shall we use for power when all the oil in the world has _______?

I thought she was famous, but none of my friends have _____ heard of her [ ]

Don’t you think it necessary that he _______ to Miami but to New York?— I agree, but the problem is _______he has refused to.[ ]