You will be able to get good marks ________.

1. A.
   while you are doing your homework by yourself
2. B.
   if you do some revision every day
3. C.
   before you begin to study hard
4. D.
   until you follow your teachers' advice

You will be able to get good marks ________.

[　　]

A．while you are doing your homework by yourself

B．if you do some revision every day

C．before you begin to study hard

D．until you follow your teachers' advice