The true descriptions for chemical changes are:
A. there are the same number of atoms before and after the change
B. the chemical and physical properties change during a chemical reaction
The other statements are not true for chemical changes:
C. the identity of the substance stays the same (this is false; the identity of the substance does change in a chemical reaction).
D. cutting down a tree is an example of a chemical reaction (this is false; cutting down a tree is a physical change, although it may eventually lead to chemical changes like decomposition).