【正确答案】 A

【答案解析】[解析] 1-4 S: Let's talk about the results of your laboratory experiment. Did you have any problems with it? B: Yes, Professor Smith. We did. S: Who's your lab partner, Bob? B: Anne Wilson. S: Well, Anne, can you and Bob go over the procedure for the class? A: Sure. First we put ten grams of crushed limestone in a bottle. S: Anything special about the bottle? B: It was a gas-collecting bottle with a one-hole stopper and bent glass tubing. S: Very good. So you put the limestone in a gas-collecting bottle. Then what? A: Then we poured in ten milligrams of hydrochloric acid, put on the stopper, and collected a bottle of carbon dioxide. S: Right, what was the method of collection? A: Water displacement. S: Good. A: Then, we lit a magnesium ribbon and put it in the bottle of carbon dioxide. B: And carbon deposits began to form on the bottom of the bottle, you see, we didn't have any problem with procedure... A: Well, we had a little problem getting the magnesium ribbon to stay lit until we could get it into the bottle. B: Okay. But we did it. The big problem was that we really didn’t understand what happened. Did the magnesium combine with the oxygen in the carbon dioxide? S: You have just answered your own question, Bob. The burning magnesium broke the carbon-oxygen bonds in the carbon dioxide, and then the oxygen combined with the magnesium to produce magnesium oxide. A: And the carbon was freed to deposit itself on the bottle. S: Exactly. [试题分析] 本题考查的是会话的目的。 [详细解答] 此类题目首先一定要听明白大概的意思，听的时候注意关键词，依据会话中“Let's talk about the results of your laboratory experiment”可以看出A为正确答案。