This is the list of answer choices is:
A. In a chemical change, no new substance is formed
B. In a chemical change, a substance changes its phase
C. In a chemical change, the molecular structure of a substance changes
D. In a chemical change, one substance dissolves into another
And the right answer is the option C. In a chemical change, the molecular structure of a substance changes.
That is true because the basic unit that remains unchanged is the atom. The atoms combine making bonds and forming molecules. So, in a chemical change tha atoms form new bonds, leading to new molecules, which is what a change in the molecular structure of a substance means.