下列哪种心律失常应视为危急情况
A.心房颤动
B.窦性心动过速
C.室性早搏,“r”落在“t”上
D.室性早搏,2~4次/min
E.窦性心律不齐
参考答案:C
直角刚杆OAB可绕固定轴O在图示平面内转动,已知OA=40cm,AB=30cm,ω=2rad/s,a=lrad/s2,则图示瞬时,B点加速度在y方向的投影为()。
A.40cm/s2
B.200cm/s2
C.-200cm/s2
D.50cm/s2
His roar was so ____ that our blood turned to ice. [ ]
A. frightening
B. frightened
C. exciting
D. excited