最易发生幽门梗阻症状的消化性溃疡是（）
A.胃角溃疡
B.胃窦小弯溃疡
C.幽门管溃疡
D.十二指肠球后溃疡
E.胃恶性溃疡
参考答案：C
The reason _____ he refused to attend the meeting was that they didn't give him an invitation earlier.
A．how
B．why
C．which
D．that
违约责任是一种()法律责任。
A．过失
B．故意
C．合同
D．欺骗
