Question

You may have noticed that when water boils, you can see bubbles that rise to the surface of the water.
a. What is inside these bubbles?
i. air
ii. hydrogen and oxygen gas
iii. oxygen gas
iv. water gas
v. carbon dioxide gas

Answer 1

You know it can't be air; there was no air to begin with.
You know the water didn't decompose so ii can't be right.
Same reasoning for why iii can't be right.
No reason to think CO2 can be right.
So what's left. Wouldn't you think water vapor would be reasonable?

Answer 2

iv. water gas