旅行社质量保证金的赔偿时效期限为（）。
A.90日
B.60日
C.30日
D.15日
参考答案：A
露天顶升航空器时规定（）.
________ a teacher, John thinks that his main duty is to help the students to become better learners. [ ]
A. As
B. By
C. About
