You can not imagine the difficulty they had ____ the problem. It isn’t ____ easy.

You look really cool in the new dress, dear. How much did you ________ it?

Not until I began to work ____ how much time I had wasted.

Amy , I would like your uncle to help me repair the computer. —Sorry, he _____help you today . He won’t come back until tomorrow.

It was back home after experiment.