In which scenario is a chemical change occurring?

A. A cup of ice cream is melting. B. A block of dry ice is sublimating.

C. A section of iron fence is corroding. D. A flask of chlorine gas is condensing.

Answer is C because each of the above cause a change in state, hence it's physical, the molecules remain same.

But corrosion is a chemical change, cause there is an addition of water and air to the regular iron molecules

the answer is A because had this question before