typical survey
参考答案：
典型调查，典型调查就是在调查对象中有意识的选择若干具有典型意义或者代表的单位进行非全面调查。
HLA分子多态性部位是
A．肽结合区
B．跨膜区
C．Ig样区
D．胞质区
E．以上都不对
Given Cov (X,Y) = 1000000. What does this indicate about the relationship between X and Y（）
A. It is p and positive.
B. It is weak and positive.
C. Only that it is positive.
