Long Before the Weather Forecast Appeared on the Nightly Local

Long before the weather forecast appeared on the nightly local news, farmers had their own way of predicting the weather. This makes sense because, after all, their livelihood depended on it. While some people might discount their predictions as mere tall tales, there is indeed some truth in many of their sayings. For instance, there is an old saying: "Frogs croaking in the lagoon means rain will come real soon." Frogs are cold-blooded amphibians, so they require moist skin and relatively high temperatures to be active. Their croaking implies that the temperature and humidity are high-and these can often precede summer thunderstorms. Far from being a pest, this creature can actually give a farmer insight into approaching weather patterns. It's probably even be more accurate than a weather forecast on the nightly news!
What is the author's purpose for writing this passage?

A) To express intense feelings about the lives of farmers
B) To persuade readers not to believe old sayings about the weather
C) To entertain readers with a story about a funny farmer
D) To inform readers that farmers' weather predictions can be accurate