下机纬密
参考答案：指织物了机后所测量的单位长度内的纬纱根数。
My friend’s flight had taken off _________ I got to the airport to see him off.
A．while
B．after
C．before
D．until
急性一氧化碳中毒时，最先受损的脏器为( )
A．心和肺
B．心和脑
C．肺和脑
D．肺和肾
