Little ______  that we were watching his every move，so he seemed to be going his own

way in this business.

A．he knew

B．he didn't know

C．didn't he know

D．did he know

对成人进行胸外按压法，压到（）后立即全部放松，使胸部恢复正常位置让血液流入心脏（放松时急救人员手掌不准离开胸壁和按压部位）。

A.2～3cm

B.3～4cm

C.3～5cm

D.4～6cm