题型：问答题 简答题 —Could you tell me _____?—Certanily. In half an hour. [ ]A. when will the high speed train arrive B. when the high speed train will arrive C. when would the high speed train arrive D. when the high speed train would arrive 查看答案
图像如图所示，请回答：
内的位移是多少？
图像）。 