丙烯在空气中的爆炸极限是()
参考答案:2.0~11.1%
It is the first time I _____ visitors since I moved to London.[ ]
A. had had
B. have had
C. have
D. had
患者,男性,62岁,胃大部切除术后行空肠造瘘。该患者饮食应采取
A.低脂肪饮食B.半流饮食C.流质饮食D.少渣饮食E.要素饮食