健脾丸的功用是
A．消食和胃B．消食导滞，清热祛湿C．行气导滞，攻积泄热D．健脾和胃，消食止泻E．行气消痞，健脾和胃
参考答案：D
Not only his parents but also his brother to the Summer Palace. They haven’t been back.
A．have been
B．have gone
C．has been
D．has gone
设关系R和S具有相同的目，且它们相对应的属性的值取自同一个域，则R-(R-S)等于______。
A．R∪S
B．R∩S
C．R×S
D．R÷S
