—This term I want to be the top student in my class.

—              .[ ]

A. Congratulations

B. Never mind

C. Of course

D. Good luck to you

A portable dry chemical fire extinguisher discharges by（）.

A.gravity when the extinguisher is turned upside down

B.pressure from a small CO₂ cartridge on the extinguisher

C.air pressure from the hand pump attached to the extinguisher

D.pressure from the reaction when water is mixed with the chemical