某化工厂工人,男,48岁,从事离子交换树脂工作12年。近来主诉咳嗽和胸痛,痰中有血丝,怀疑其患职业肿瘤。采集职业史时应注意何种毒物的接触史
A. 石棉
B. 铬酸盐
C. 氯甲醚
D. 砷
E. 苯
查看答案
Had he worked harder, he ______ the exams.
A. must have got through
B. would have got through
C. would get through
D. could get through
A是3阶矩阵,α是3维列向量,使得P=(α,Aα,A2α)是可逆矩阵,并且A3α=3Aα-2A2α,设3阶矩阵B,使得A=PBP-1,则|A+E|=()。
A. 4
B. -4
C. 2
D. -2
在某人群A和B两组中进行大肠癌的筛选,假定筛选试验的灵敏度和特异度都为70%,但A人群患病率为10%,B人群患病率为5%,则下列哪个结论是正确的
A. 在A人群中试验的真实性高于B人群
B. 在A人群中试验的可靠性高于B人群
C. 在A人群中试验的阴性预测值高于B人群
D. 在A人群中试验的阳性预测值高于B人群
E. 在A人群中试验的Kappa值高于B人群
The helicopter ______ a light plane, and one pilot was seriously injured and the other missing.
A. coincided with
B. collided with
C. ran into
D. joined to