Hb氧饱和度是指( )

A．Hb氧容量占Hb氧含量的百分比
B．Hb氧含量占Hb血氧容量的百分比
C．溶解氧量占Hb氧容量的百分比
D．溶解氧量占Hb氧含量的百分比

The light is still _________. Mr. Green _________ at home now. [ ]

A. on, can be

B. down, may be

C. on, must be

D. up, can't be