~Chemistry

B. Sulphur dioxidetoxic should be re-written as Sulphur dioxide toxic
A. Potassium explosive
Incorrect. Potassium is flammable and corrosive, not explosive.
B. Sulphur dioxide toxic
Correct. Sulphur dioxide is toxic.
C. copper(II) sulphate irritant
Incorrect. Copper(II) sulphate is harmful and dangerous for environment.
D. Carbon monoxide flammable
Incorrect. Carbon monoxide is highly flammable and toxic.
Hence combination B is correct.

Contradictary for the explanation of choice D.

I think that you have a typing mistake.
"dioxidetoxic" should be in to two words "dioxide toxic"
So the answer is B.