减压阀安装使用时，阀的进、出口处一般要伴装（）。
A．安全阀
B．止回阀
C．截止阀
D．疏水阀
参考答案：C
Traditional folk arts of Tianjin like paper cutting ________ at the culture show of the 2010 Shanghai
World Expo.[ ]
A. are exhibiting
B. is exhibiting
C. are being exhibited
D. is being exhibited
以下关于Ⅰ型变态反应的描述错误的是（）
A.毛细血管扩张
B.毛细血管通透性增加
C.平滑肌收缩
D.腺体分泌减少
