Answer : The question is to write the elements alphabetically and seperating them with commas.
So in this case for your question of Fireworks , K

,
The answer will be
K, N, O.
You have to just differentiate the elements and write them according to the alphabetical order.
Answer:

Explanation:
Hello!
In this case, according to the chemical reaction:

We can evidence the 2:1 mole ratio between hydrogen and tin, thus, we perform the following stoichiometric setup to obtain the mass of produced tin:

Best regards!
I would suggest convection !!!