Come and see me whenever ___________

It was by making great efforts_______she caught up with other students.

I’m surprised that John is only 25. I thought he was________ , for he seems to be in his thirties.

14．How can you cross the river _________ by swimming?

Now lots of teenagers spend a lot of timeplaying computer games.——Yes. Teachers and their parents shouldprevent them ______________ too much.