Some intelligent and successful people find _____ difficult to succeed in language learning. 

Health experts believe that even a little exercise is far better than _____at all. 

It makes good sense to buy a large packet because ________ will work out cheaper in the end.

–What do you think of the man？--I find _____ difficult to work with him. 

—Which type of car do you like better?—       ．They are both expensive and high emission（高排量）．