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

Have you heard the latest news?—Yeah, Xi Jinping became new president of China.

Hurry up, Mike. You must get to the airport an hour before the plane________.

How did the accident happen? —You know, it ________difficult to see the road clearly because it_________.

Sam spends two hours _______ his homework every day.