1.  How much do you know about him?

2.  However, only when we get familiar with someone can we know exactly how he or she is like.

3.  "Who knows the answer?

4.  Who knows how we talked before our voice got un-Brooklyned.

5.  However, who knows the key to success?

6.  As for reasons, who knows?

7.  However some people don't know the meaning of it.

8.  Except the way of online meeting, how can they know their colleague?

9.  However, do you know how to choose a real friend?

10.  Why don't people in the rural area know what nuclear means?