颈部气管闭合性创伤症状可表现为()。
A.呼吸困难
B.声嘶
C.纵隔气肿
D.咳嗽,大出血
E.疼痛,可放射至同侧耳部
参考答案:A, B, C, D, E
下列生物中属于竞争关系的是 [ ]
A.水稻和稗草
B.猫和老鼠
C.人和猪
D.蚂蚁和蚱蜢
Helen always helps her mother even though going to school ____ most of her day. [ ]
A. takes up
B. picks up
C. gives up
D. puts up