确诊溃疡活动性出血的最可靠的方法是（）
A.胃液分析
B.X线钡餐检查
C.大便隐血
D.急诊胃镜检查
E.血色素测定
参考答案：D
When and where the meeting will be held____.[ ]
A. has decided
B. had decided
C. has been decided
D. is decided
滚珠轴承( ) A．22 B．21 C．23 D．24
