13. --Hi, Lydia. Are you going to the concert on Friday? - -I’d like to. But there are so many problems ____.
We must notice the use they are the new energy.
Since you have lots of spare time, why not _a foreign language?
Unfortunately, not everyone has realized the important part that healthy diets in their daily life.
I was on the point of talking to the professor when John .
It is said that he will his business to his son when he retires.