如图所示,下列判断正确的是
A.由甲图可以知道周期
B.由乙图可以知道周期
C.甲图是波动图象,乙图是振动图象
D.甲图是振动图象,乙图是波动图象
BC
改错,下列句子均有一处错误,找出来,将正确的句子写在横线上。
1. It's a old, old story.
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2. There are two pair of skates.
3. Danny walk to school every day.
4. These are my boot.