IgM明显增高常见于()
A.类风湿关节炎
B.多发性骨髓瘤
C.支气管哮喘
D.巨球蛋白血症
E.获得性体液免疫缺陷病
参考答案:D
事故停机中导水叶剪断销剪断,为什么制动后不允许撤出制动?
Although this _____ sound like a simple task, great care is needed. [ ]
A. must
B. may
C. shall
D. should