题干
— May I speak to Jim Green?
— _________ He is in the supermarket now.
A：Who are you speaking?
B：Yes, of course you can.
C：Could you call him later?
D：This is Jim Green.
答案(点此获取答案解析）
C
＜
，某时刻在P点为两列波的波峰与波峰相遇，则以下叙述正确的是（ ）