单选题 What is the tone of the following passage? There is no easy solution. But simply being aware of your personal clock can help you find the best times for exercise, socializing and even important conversations. In general, it's best to bring up serious topics around 5 P.m., because people tend to be in a better mood in the early evening. By 11, though, they tend to be tired, making a heated discussion—and not its resolution—more likely to end up in their long-memory. These changes can be small, but they can have a transformative effect on health and well-being