题目

阅读理解The Dragon Boat Festival is very popular in China. It comeson the fifth day of the fifth month according to Chinese calendar. On that day,people eat special food-zongzi. It is also known for dragon boat races. Thedragon boat race is the most popular activity during the festival, especiallyin South China. A dragon boat looks like a dragon, and is painted in red, white,yellow or black. Usually, a dragon boat is twenty to forty meters long, andneeds twenty people to row. Boatmen row the boat in cadence(节奏)with the drumbeats, asthe captain in the front of the boat waves a small fla 做阻尼振动的物体先后两次经过同一位置时，下列说法正确的是 A． 有相同的机械能 B． 有相同的势能 C． 有相同的动能 D． 有相同的动量