判断：水痘病毒侵入人体后，淋巴细胞产生抗体，抗体消灭抗原后，体内不再存在抗体。（  ）

小明一家三口人外出旅游乘火车，每张火车票216元，回来还乘火车，这次旅游火车票一共花了多少钱？

从方框中选择合适的选项补全对话。

A: Where have you been, Li Hai? I called you, but you weren't in.

B: ____

A: ____

B: I found that the factory was pouring waste water into the river near it. Lots of fish have died.

A: ____

B: Do you think “Greener China” can do something?

A: ____ if they know about this thing, they will prevent it. Let's write to them at once.

B: ____ I think everything will become better.

八棱柱有____个顶点，____条棱，____个面．