A:y=cos2x
B:y=2|sinx|
C:
D:y=﹣cotx
After practicing for several months, I can swim much________now.
It is bad manners to s____ your legs while eating.
滑动变阻器的原理是改变电阻丝____ 来改变接入电路的电阻.
种子萌发必需的外界条件不包括( )