You should not go rafting ________ you know how to swim.
| A．if | B．if not | C．when | D．unless |
This dance is known _______ country music.
A. perform by B to be performed with
C. to be performed to D. being performed in
. How can you expect to get everything ______ you never give?
| A．in case | B．even if | C．unless | D．when |
Meeting my uncle after all these years was an unforgettable moment, ______ I will always treasure.
| A．that | B．one | C．it | D．what |
. The country has already sent up three unmanned spacecraft, the most recent ______ at the end of last March.
| A．has been launched | B．having been launched |
| C．being launched | D．to be launched |
. What the doctors really doubt is ______ my mother will recover from the serious disease soon.
| A．when | B．how | C．whether | D．why |