盆底肌有（）和（）两块扁肌。
参考答案：肛提肌；尾骨肌
—They say there's a new restaurant nearby.
—Yes, and it ____ for no more than a week. [ ]
A. has been open
B. opens
C. is opening
D. is opened
使用SQL语句增加字段的有效性规则，是为了能保证数据的
A．实体完整性
B．表完整性
C．参照完整性
D．域完整性
