属于线性相关的是（）
A.
B.
C.
D.
参考答案：A
解析：
B是弱正相关，CD是非线性相关。
When I met him the other day, it was the first time we _____ each other since we were at school.[ ]
A. saw
B. had seen
C. were seeing
D. have seen
男性，60岁，有高血压病史，于夜间发生阵发性呼吸困难伴喘鸣，并咳粉红色泡沫样痰。应考虑为（）
A.支气管哮喘
B.心源性哮喘
C.气管异物
D.肺气肿
E.呼吸衰竭
