According to the analysis of life experience, it is not difficult to find that when looking in the mirror, although the image in the mirror is upright, its left and right are upside down. There are several ways to summarize this kind of topic: first, look at the picture from the back of the paper with the conventional reading method, and it is easy to read that the time at this moment is 3: 40. Method 2: Read from front to back counterclockwise. The numbers on the map are arranged counterclockwise from small to large, so it is not difficult to read that the time is 3: 40. Method 3: "Twelve Deduction Method" reads the time on the clock according to the conventional reading method, and then subtracts this time by twelve, which is the actual time. The regular reading time is 8:20, and the actual time is 12:00-8:20=3:40. Method 4: One of the characteristics of the "symmetry method" plane mirror imaging is that the image and the object are inverted from left to right. According to the properties of the axisymmetric image, it can be concluded that the time is 3: 40 and the answer is C. This topic belongs to the practical application of the imaging characteristics of the plane mirror. Several common methods to solve the clock problem are listed in the analysis, which should be analyzed carefully. You can use these methods directly when you encounter similar problems.