___ you know the rules of swimming, you will be able to swim well.
| A．Before | B．While | C．Though | D．Once |
Being League members, ___ we ought to work hard at our lessons;___ we ought to take an active part in social activities.
| A．on one hand…on other hand | B．on the one hand….on the other hand |
| C．on the one hand…on the other | D．B and C |
___ the clock structk twelve. I got home with my brother.
| A．As | B．While | C．When | D．Since |
____ for a bus, I was reading a magazine.
| A．While was waiting | B．While I waiting | C．While I am waiting | D．While waiting |
Knowing how long the test would last, the students who finished ____ back and waited until the end of the exam.
| A．settle | B．settled | C．settling | D．to settle |