One of the disadvantages of using carbon dioxide to extinguish a fire in an enclosed space is （）.

A.the "snow" which is sometimes discharged along with the gas is toxic
B.prolonged exposure to high concentrations of  C0₂ gas causes suffocation
C.rapid dissipation of the C0₂ vapor
D.the C0₂ gas is lighter than air and a large amount is required to extinguisha fire near the deck