人工胸外心脏按压的深度是（）
A.1～2cm
B.5～6cm
C.7～8cm
D.3～5cm
E.4～6cm
参考答案：D
It was really ________ of your brother not to play the guitar while you were preparing your lessons.
A．typical
B．generous
C．considerate
D．determined
减压塔内不凝气量增加，减顶真空度（）。
A.下降
B.不变
C.升高
