A:b摆动,a、c摆不动
B:a、b、c摆都动,且周期与d摆的相同
C:a、b、c摆都动,且振动幅度与d摆的相同
D:a、b、c摆都动,且c摆的振动幅度最大
—Why are you standing here, Tom?—I can't see the blackboard clearly. Two tall boys are sitting ____ me.
2(xy+13y2)−13(2y2+7yx)−3 ,其中 x=−1,y=2
青春期是指由儿童逐渐发育成为成年人的过渡时期。下列关于青春期的叙述,不正确的是( )