What is the sum of all coefficients for the combustion of one mole of propane?

___ ${{\text{C}}_{\text{3}}}{{\text{H}}_{\text{8}}}{\text{(g)}} +$ ___ ${{\text{O}}_{\text{2}}}{\text{(g)}} \to$ ___ ${\text{C}}{{\text{O}}_{\text{2}}}{\text{(g)}} +$ ___ ${{\text{H}}_{\text{2}}}{\text{O(l)}}$

A.     8

B.     12

C.     13

D.     15

C

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