As we were asleep, ＿＿ of us heard the sound .

— Which of these two books will you take?—I will take ______ in case the trip is boring.

---Which book do you think is the most useful to my studies?---________, as long as you read it. In fact, they are out of date.

The young man is very clever; he may be     Edison.

. If I were ____younger, I would do ____ I am interested in.