消化道出血最常见的病因是
A．消化性溃疡
B．肝硬化门静脉高压
C．胃结石
D．胆道出血
E．慢性胃炎
参考答案：A
Where were you at supper time? I _____ for you to join me. [ ]
A. waited
B. had waited
C. have been waiting
D. was waiting
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