如图所示，质量为50kg的物体A置于粗糙的水平地面上，用两个滑轮按图连接，当水平

A: Hi, Alice! Where did you go on vacation?

B: I went to Sanya with my family. 小题1:_____________________________?

A: Me? I didn’t go anywhere. I just stayed at home every day.

B: Oh, it souds a little boring.

A: Yeah, I think so. 小题2:____________________________________?

B: We went there by plane.

A: 小题3:_________________________?

B: Yes, of course! We all have a very good time. You know I love taking photos, so I took a lot of photos on the beautiful beach!

A: 小题4:________________________! Can you show me some of your photos?

B: No problem. I will take the photos to you tomorrow.

A: Thank you.

B: 小题5:_________________________. See you tomorrow.

A: See you!

将标号为1，2，…，9的9个球放入标号为1，2，…，9的9个盒子里，每个盒内放一个球，恰好3个球的标号与其所在盒子的标号不一致的放入方法种数为（　　）

A．84

B．168

C．252

D．504

以下程序输出的结果为______。 main() { char*dlpha[6]={"ABCD"，"EFGH"，"IJKL"，"MNOP"，"QRST"，"UVWX"}； char*p； int i； p=alpha； for(i=0;i＜4;iff) printf("%s",p[i]) }

A．ABCDEFGHIJKL

B．ABCD

C．ABCDEFGHIJKLMNOP

D．AEIM

质量为300g的水，温度由100℃降低到50℃，放出的热量是______焦．【c_水=4.2×10³J/（kg•℃）】

经典型预激综合征的心电图特点不包括（）。

A.P-J间期正常

B.QRS增宽≥0.12s

C.QRS起始部有delta波

D.PR间期<0.12s

E.无ST-T改变