Which of the following are examoles of combustion reactions

1. CH4 (g) + O2 (g) --> CO2 (g) + H2O(I)
2. CaO(s) + CO2 (g) --> CaCO3 (s)
3. PbCO3 (s) --> PbO (s) + CO2 (g)
4. CH3OH (I) + O2 (g) --> CO2 (g) + H2O (I)


a.) 1 and 4
b.) 1,2,3, and 4
c.) 2,3 and 4
d.) 2,3, and 4
e.) 3 and 4

(1)&(4) are combustion reactions (something reacting with oxygen)...so (a) is your answer.