I don’t think I can work_____ the math problem.—Think hard, and you can come up _____ the answer.

the long-term effects of global warming some believe that the damage has been done, ______________________.

I can’t bear ________, so I hope you can come on time.

You can only borrow two books _______ if you don’t have a library card.

He hurried back home _________ his schoolbag.