Listen to part of a lecture in a biology class. The professor is discussing animal communication.
Professor: Today, we're going to talk about the various ways animals communicate, and I want to focus on a fascinating example: the waggle dance of honeybees. When a foraging bee returns to the hive, it performs a series of movements on the vertical surface of the honeycomb. The angle of the dance relative to gravity indicates the direction of the food source in relation to the sun. The duration of the waggle run, the straight part of the dance, communicates the distance. For instance, a longer waggle run means the food is farther away. Interestingly, bees can also adjust their dance based on the quality of the food source. If the nectar is particularly rich, the bee will repeat the dance more vigorously and for a longer period, encouraging more recruits to follow. However, this communication system isn't perfect. Environmental factors, like wind or obstacles, can distort the information, leading some bees astray. Still, it's a remarkable example of symbolic communication in the animal kingdom.
❓ 题目 According to the professor, what does the duration of the waggle run indicate?
A. The direction of the food source relative to gravity