He turned ________ the radio because his father was asleep.
A．on B．down C．up D．over
The accident took place ________ a cold February evening.
A．on B．in C．at D．for
______ the maths problem is difficult， I'll try very hard to work it out.
A．Though B．When C．Before D．After
Don't hurry. The bus won't start ______ everybody gets on.
A．since B．as C．until D．when
I didn't buy the dictionary yesterday _____ my aunt would give me one.
A．until B．because
C．if D．before
We can't do it ______ your help.
A．with B．of
C．under D．without
