听力原文：M: It looks like we are going to have a shower at any minute now. W: I think so too. Isn't strange how you can sense it? M: I know what you mean. W: Look at the clouds in the sky. Whenever they seem dark and low like this,you know it's going to rain, or look at the object that's far away, if it seems clear to you, it's probably going to pour. M: Yes. And everything seems to have a stronger smell to me then. W: I know, and people often say it's going to rain when they have aches and pains in certain parts of their body. My mother always complains that her knee hurts just before a storm. M: And have you noticed how the animals react before a storm? W. Sure, horses and cows will seem to go a protected area and huddle together. M: Yah, but with all these sensible signs, how come we aren't carrying our umbrella with us now? What is the main topic of the conversation?