房屋租赁是一种( )行为，必须依照法律规定履行必要的程序后才能成立。
A．要式 B．非要式C．经济 D．合同
参考答案：A
Activities that are related and shown as a single, aggregate activity reported at a summary level are called ______ .
A．master schedule
B．hammock
C．WBS
D．hanger
下列药物中有两个手性碳原子的是
A．利福平B．呋喃妥因C．乙氨丁醇D．小檗碱E．青霉素
