I just don’t understand ______ that leads to so many teenagers becoming addicted to playing computer games.

—I’ve read another book this week.
—Well, maybe __ is not how much you read but what you read that is important.

—Is it that Jack often plays computer games    makes his parents worry about him ?
—Yes , I think so .               

_______ is not the story itself but the lovely characters in it _______ make children interested in the cartoon.

_______ it two days ago when you arrived home late that you came across her?

It was about 600 years ago _______ the first clock with a face and an hour hand was made.

It was        the quality of life in the future         I took this training course，not just to make more money.

It’s not how much we do but how much love we put into what we do _____ benefits our work most.

It was along the Mississippi River _________ Mark Twain spent much of his childhood.

I really don’t know ___ ___I kept the secret papers.