横浇道的截面形状，在浇注大型铸钢件时多采用（）。
A.梯形
B.圆顶梯形
C.圆形
D.扁平形
参考答案：C
The flu is believed _____ by viruses that like to reproduce in the cells inside the human nose and throat. [ ]
A. causing
B. being caused
C. to be caused
D. to have caused
肺结核干酪样肺炎X线显示的空洞特点是（）
A.薄壁空洞
B.厚壁空洞
C.虫蚀样空洞
D.不规则空洞
E.偏心空洞
