羊水栓塞是由羊水中的抗原成分引起：
A．I型变态反应B．Ⅱ型变态反应C．Ⅲ型变态反应D．Ⅳ型变态反应E．不是变态反应
参考答案：A
A.亚洲 B. 非洲 C. 欧洲 D. 美洲
— Do you know anything about the school?
— Yes. In fact, this is the third time I _____ here. [ ]
A. was
B. came
C. have been
D. will come
