问卷调查法局限性之一是（）问题，如果太低会影响其代表性。
A.取样
B.回收率
C.信度
D.效度
参考答案：B
—Who wants to answer the question?
—Let me . [ ]
A. to have to try
B. have a try
C. trying
D. is trying
浇筑梁体封端混凝土之前，应注意哪些问题？
