《雨打芭蕉》是一首由（）三重奏的民间乐曲。

根据下面对话中的情景，在每个空白处填入一个适当的语句，使对话恢复完整。

( J=John  L=" Li" Lei)

J: Hello,Li Lei!

L: Hi, John. Can you come and play football with us on Sunday morning?

J: Sorry, I can’t.____ 小题1:___________________.

L: A piano lesson? Well, how about afternoon?

J: ___小题2:________ . You know, he has a farm in the village. He asked me to help him.

L: Go to the farm? That sounds great.___小题3:________?

J: Certainly. That’s very good. Uncle must be very happy to see you.

L: _小题4:_____________?

J: Nothing. But you have to put on your old clothes.

L: OK. ___小题5:__________?

J: Let’s meet at my house at 2:30 pm.

L: OK. See you.

（ ）

转炉炼钢厂供中板厂板坯规格：220×1500×6700（mm），共12块钢板。该批板坯在生产中的轧废为5.54吨、烧损为2%、切损为2%，检验判出各类缺陷：分层5.31吨，结疤3.51吨、瓢曲3.2吨。请计算该批钢板的成材率。（比重按7.85g/cm3）

M型超声心动图中，二尖瓣最早完全关闭点是（）。

A.C点

B.D点

C.E点

D.F点

E.B点

净电荷