Which letter means that oil-spilling has happened?（）

A. Dry extinguisher
B. Power extinguisher
C.A+B
D. CO₂ extinguisher

A. Emergency power supply.
B. Quick-close device.
C. Emergency squad.
D. derricks.

A. Lifeboat.
B. Life-raft .
C. Life rail.
D. Lifebuoy.