Question

Which of the following is produced when propane (C3H8) is combusted completely? (2 points)

H2O
CO
O2
H2

Answer 1

Note complete combustion excess of oxygen, is different from incomplete combustion which would produce carbon monoxide.

The formula for complete combustion is this:

C3H8 + O2 = CO2 + H2O

H2O would be your answer

Answer 2

CO is the product of incomplete combustion.

While O2 is your reactant, can't be your product just doesn't make sense.

Answer 3

Apologies that formula above isn't balanced
It should be this

C3H8 + 5O2 = 3CO2 + 4H2O