书写护理记录单时，_______用蓝钢笔记录，_______用红钢笔记录。
参考答案：7am以后｜7pm以后
In the last two years, they _____ three major concerts. [ ]
A. have had
B. has had
C. made
D. have
在流体管中，闸阀的开度为50%时，其阻力系数约为（）。
A.3.2
B.1.8
C.1.1
D.0.6
