消化性溃疡发生癌变的表现()
A.消化不良症状加重
B.疼痛失去原有规律性
C.大便隐血试验持续阳性
D.胃酸分泌增多
E.进行性消瘦
参考答案:A, B, C, E
He was disappointed to find his suggestion ____ .[ ]
A. been turned down
B. turned down
C. to be turned down
D. to turn down
直流输电双极系统的接线方式有哪几种()
A.双极两端中性点接地方式
B.双极一端中性点接线方式
C.双极带金属中性点一端接线方式
D.双极两端中性点不接地方式