VB 6.0中，ADO数据控件用于连接数据源的属性是______。

A．SELECT Sname FROM S，SC，C WHERE Sno=SSno AND SCno=Cno AND Teacher=‘LIU’AND Ssex=‘F’
B．SELECT Sname FROM S WHERE Ssex=‘F’AND Sno IN (SELECT Sno FROM SC WHERE Cno IN(SELECT Cno FROM C WHERE Teacher=‘LIU’))
C．SELECT Sname FROM S WHERE Ssex=‘F’AND EXISTS (SELECT* FROM SC WHERE SSno=Sno AND EXISTS (SELECT* FROM C WHERE Teacher=‘LIU’))
D．SELECT Sname FROM S WHERE Ssex=‘F’AND EXISTS(SELECT* FROM SC WHERE SSno=Sno AND EXISTS (SELECT* FROM C WHERE Cno=SCno AND Teacher=‘LIU’))

A．调度分为串行调度和并发调度
B．串行调度的特点是一个事务的所有操作都执行完后才开始执行另一个事务
C．多个事务的调度必须保持每个事务的操作在事务中的执行顺序不变
D．并发调度中不同事务的操作不可以交叉执行