自动充气式气囊连接氧源，不加储氧器，可得到约（）浓度的氧。

A.30%
B.25%
C.60%
D.21%

A.85%
B.90%
C.95%
D.100%

A.0.80~0.85
B.0.85~0.90
C.0.90~0.92
D.0.92~0.95