17.The heating value of a fuel is related chiefly to its specific gravity and its sulfur content. As the specific gravity of oil increases, the carbon-to-hydrogen ratio increases, which results in the relatively less hydrogen and a consequent decrease in the heat released during combustion. Therefore, .
(A)the increase of specific gravity of fuel increases the heat released during combustion
(B)the increase of specific gravity of fuel reduces the heat released during combustion
(C)the increase of carbon-to-hydrogen ratio of fuel increases the heat released during combustion
(D)the increase of carbon-to-hydrogen ratio of fuel increase the hydrogen content in oil fuel