最长停留期
参考答案：是指旅客在目的地的最长停留期限。
Many of the things that_________ thought useless_________ man today.[ ]
A. used to be; used to serve
B. were used to being; are used to serving
C. were used to be; are used to serve
D. used to be; are used to serve
斗轮机回转机构不动作的原因有哪些？
