左心功能不全的主要症状为（）
A.咳血
B.胸痛
C.呼吸困难
D.少尿
E.咳嗽、咳痰
参考答案：C
While Helen _____ along the river after supper, she ____ a wallet lying on the roadside.
A. was walking; was finding B. walked; found
B. walked; was finding D. was walking; found
一个完整的空调系统的组成部分不包括( )。
A．被调对象B．干燥剂C．空气处理设备D．空气输配系统
