接头拦截面访的缺点之一是（）。
A.问卷长度比较长
B.费用比较高
C.效率不高
D.搜集的数据对总体的代表性不强
参考答案：D
下列哪个房室增大后，食管受压后移（）
A.左房
B.右房
C.左室
D.右室
E.以上均不是
Mathematics as well as physics _______ very important to any student who wants to enter a good university. [ ]
A. are
B. is
C. was
D. were
