—I'll call you ______ I arrive in Shenzhen． —Thanks, and good luck．

What does "quake" mean _____ in the word "earthquake"?

______ is well known to everyone, I should say, is that a man becomes learned by asking questions.

_________ I picked up the receiver, I realized that someone had dialed the wrong number.

It is a difficult problem for high school students      they can properly use the Internet．