From another answer, it is most likely E. Horizon. Hope this helps!
Substances that will make a salt when combined is Soda and Ammonia
Your answer is the last option, the explosion of fireworks. This is because all of the other options are physical changes because they don't change the substance, they only affect it in some way. However the explosion of a firework clearly changes a substance inside the initial 'rocket' into fireworks.
I hope this helps!
The answer is zinc sulfite
