题目

如图所示，A球振动后，通过水平细绳迫使B、C振动．下列说法正确的是（ ）                                                                                                                                                                                                                                                             　   A．  只有A、C两球的振动周期相等 　   B．  C球的振幅比B球的振幅小 　   C．  C球的振幅比B球的振幅大 　   D．  A、B、C三球的振动周期相等                                                                                                                                         答案：CD

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