上消化道出血的常见病因有（）
A.消化性溃疡
B.食管静脉曲张
C.胃底静脉曲张
D.贲门失弛缓
E.胃癌
参考答案：A, B, C, E
某校组织同学们去鸟巢参观，如果一次进7个学生，6次能进多少个学生？
— She didn't come to school yesterday, did she?
— ______, though she was not feeling very well.[ ]
A. No, she didn't
B. Yes, she was
C. No, she wasn't
D. Yes, she did
