通过操纵变数以测量传播效果的实验性研究而构成了态度改变研究开端的是（）.
A.霍夫兰
B.李普曼
C.施拉姆
D.拉扎斯菲尔德
参考答案：A
带运包裹对占用的包房铺位应如何收费？
—How you've changed! You _____ very short.
—But I am not sure if I am taller than you now. [ ]
A. are sure to be
B. use to be
C. are
D. used to be
