气管插管的套膜囊内注入3~5ml空气,其目的是防止:
A.局部血液循环障碍
B.损伤气管粘膜
C.插管周围漏气
D.痰液阻塞呼吸道
E.口鼻分泌物流入呼吸道
参考答案:C
设有点A(1,2,3)和B(2,-1,4),则线段AB的垂直平分面的方程为( )。
A.2x+4y-z+1=0 B.2x+2y-3z-7=0C.2x-6y+2z-7=0 D.2x+ 6y-2z+7=0
Don't ___ _ loudly in the classroom. [ ]
A. talk
B. talks
C. talking
D. to talk