问卷法的缺点之一是邮寄问卷回收率低，而且不了解被调查者不回答的原因。
参考答案：对
Eisenmenger综合征（）
A.肺性发绀
B.心性混合性发绀
C.淤血性发绀
D.缺血性发绀
E.混合性发绀
The book is here somewhere, but I couldn't it just now. [ ]
A. put my hands on
B. keep my hand in
C. lay my hand on
D. try my hand at
