1.At midnight he heard a strange sound．半夜里他听到一种奇怪的声音。Light travels much faster than sound．光的传播速度比声音快
1.At midnight he heard a strange sound．半夜里他听到一种奇怪的声音。
Light travels much faster than sound．光的传播速度比声音快得多。
2.The girl has a beautiful voice．那女孩嗓音很美。
They are talking in low voices．他们正小声交谈。
温馨提示：
