成人肠套叠常见的原因是（）
A.畸形
B.肠肿瘤
C.剧烈运动
D.饮食习惯改变
E.肠道炎症
参考答案：B
It's clear that management ____ developing production in factories. [ ]
A. play an important role in
B. plays an important part in
C. play a joke on
D. plays a trick on
常用平喘药的分类如下
A．抗过敏平喘药
B．抗胆碱药
C．β受体激动药
D．茶碱类
E．糖皮质激素
