信源
参考答案：
通信过程中产生和发送信息的设备或计算机。
—Hello! This is Henry speaking. I'd like to speak to your father.
—Sorry, he has _____ Shanghai. [ ]
A. been in
B. been to
C. gone to
D. come to
胃十二指肠溃疡病出血的特点，错误的是（）
A.呕血前常有恶心
B.量大的出血可解鲜血便
C.短期内失血超过800ml，可出现休克症状
D.多数患者只有黑便而无呕血
E.是上消化道大出血最常见的原因
