A: What do you ____ Halloween?

B: It's on October 31.

A: Yes. But do you know what people do on that day?

B: Of course. They ____ and dress up.

A: I hear that children love Halloween best.

B: Yes. Because they can play a game called “trick or treat” then.

A: How do they do that?

B: They paint their faces, ____ their neighbours' doors and shout “trick or treat”. If people don't give them any candy, they usually ____ them.

A: That's really interesting. Do people have a party on Halloween?

B: Yes, usually in the evening. People ____ and enjoy nice food.

某同学利用打点计时器做实验时，发现实验数据误差很大，怀疑电源的频率不是50Hz，采用如图甲所示的实验装置来测量电源的频率．已知砝码及砝码盘的质量为m=0.1kg，小车的质量为M=0.4kg，不计摩擦阻力，g取10m/s²．图乙为某次记录小车运动情况的纸带，图中A、B、C、D、E为相邻的计数点，已知相邻的计数点之间还有三个点未画出．