题目

 补全对话。 阅读下面对话，从方框中选择适当的句子补全对话（其中有两项是多余的）。 (In the Science Museum) A: Wow!     1     B: Yes, I’ve learned a lot about ancient Chinese inventions. A: Look, what’s that thing with three legs? B:     2    It was used in the old days in China. A: What was it used for? B:     3    It’s made of metal. A: Yeah, oh... A teapot.     4   When the bowl was filled with hot water, the wine in the pot   would get warm. B: That’s a good idea. A:     5     B: OK, let’s go. A. It在等差数列中，，设数列的前项和为，则（ ）A. 18 B. 99 C. 198 D. 297