W: Have you ever looked really closely at the snowflakes?
M: Sure, but they usually melt too fast for me to get a close look. Why do you ask?
W: [ 12 ] [ 13 ] I'm just curious. I was reading an article about the formation of snowflakes, and I realized that I had never paid much attention to them before.
M: Well, there is a big variety, isn't there?
W: Yeah, but they all have one of the three basic forms: hexagonal columns, thin hexagonal plates and the branching star-shaped form.
M: I wonder why the forms are different, maybe because ice starts to form on dust particles with different shapes.W: Well, I thought it might have something to do with the water saturation of the air. But we're both wrong. [ 14 ]The author of this article did extensive research and concluded that the shape of snow crystals is largely controlled by the temperature of the air. For example, the feathery star-shaped snowflake that everyone thinks is typical occurs only at a specific temperature.
M: Doesn't the relative humidity have anything to do with the shapes?
W: Apparently not. The effect of super saturation is simply to alter the growth rate. The greater the saturation, the faster the snowflakes form.
M: Wow, [15] next time it snows, I'll make a point of taking a close look.
What are the two persons talking about?
【听前预测】
1．四项均以疑问词开头(whether，how，what，where)。
2．四项均含有与雪有关的词i(snowflakes，snowstorm)。
结论：本题可能问某人正在研究什么问题，或者对话中的两人正在讨论什么问题，与雪有关。
【解析】题干问对话中的两人正在讨论什么问题，一般情况下，我们在对话开头就可以找到关于话题的线索。女士问男士是否注意观察过雪花，并说她最近读了一篇关于雪花形成的文章。在接下来的对话中，他们谈到了造成雪花形状不同的因素。故选B。