Which of the Following Is Not an Example of a Physical

Which of the following is not an example of a physical change?

A) Ice melts when warmed.
B) Dry ice sublimes (converts from a solid to a gas) at room temperature.
C) Liquid nitrogen converts to a gas at room temperature.
D) Blue copper sulfate crystals dissolve in water to form a blue solution.
E) When hydrogen and oxygen gas are mixed in the presence of a spark, water is formed.