心肺复苏时胸外按压和人工通气的比率()
A.30:2
B.15:2
C.5:1
D.2:30
E.2:15
参考答案:A
— Is Jack on duty today?
— It ____ be him; it's his turn tomorrow. [ ]
A. must's
B. won't
C. can't
D. needn't
列车运行时,母车发电机发出三相交流电经主整流器整流后变成直流电。一路经控制箱B+给蓄电池充电;另一路经控制箱()线到配电盘主开关,给本车用电器供电。
A.J
B.K
C.L
D.M