A:这列波的周期为0.5
B:再经过0.4s,质点P第一次回到平衡位置
C:再经过0.7s,x=9m处的质点Q到达波峰处
D:质点Q到达波峰时,质点P恰好到达波谷处
Hold on to your dreams, __________ one day they may just come true.
—When will your new book ________ ?
—Probably in December.