20 12, 1 1 year 10, leping city will hold the 20th anniversary celebration. The following scenes contain chemical changes: A. Setting off fireworks B. Balloon rising.

A, fireworks have new substances, which belong to chemical changes. Correct;

B, there is no new substance produced during the balloon lift-off, which is a physical change. Mistakes;

C, there is no new substance generated in the process of colorful flags flying, which belongs to physical changes and errors;

D, there is no new substance generated in the process of sound, which belongs to physical changes. Mistake.

So choose a.