在关系运算中,______运算是对两个具有公共属性的关系所进行的运算。
参考答案:自然连接
旅行社自交纳或者补足质量保证金之日起三年内未因侵害旅行者合法权益受到行政机关罚款以上处罚的,旅游行政管理部门应当将旅行社质量保证金的交存数额降低______,并向全社会公告。
A.20% B.30%C.50% D.100%
— What's wrong, Mary? You look sad.
— Oh, nothing much. In fact, I _____ of my English test. [ ]
A. think
B. was thinking
C. will thing
D. would think