单项选择题 波的传播需要荷载物（ ） A、正确 B、错误

未知题型 听力原文：Q: what is the boy going to do?(11)A.To go to the school dining hall with the girl.B.To eat the sandwich his mother has made for him.C.To have lunch with the girl at the restaurant.D.To drink a glass of water only.

未知题型 下列哪一项不属于单向时间取向人的特征（）。