四神丸主治证的病机是（）
A.肾虚精关不固
B.肾气不足
C.脾不统血
D.心肾两虚，水火不交
E.脾肾阳虚
参考答案：E
Look! Tina is ___________ in the lake and her parents are ___________. [ ]
A. swims, boat
B. swiming, boating
C. swimming, boating
在下列4个选项中，不属于基本关系运算的是_______。
A．连接
B．投影
C．选择
D．排序
