The correct answer is C: It is converted into heat. Power lost in a feed line is converted into heat. Feed line losses occur due to resistance in the conductors and dielectric losses in the insulation. When RF power encounters this resistance, it's converted to heat energy, just like current through a resistor. This heat is dissipated into the surrounding environment. For amateur radio operators, understanding feed line losses helps explain why some power doesn't reach the antenna and why certain feed lines are better than others. Low-loss feed lines minimize this heat generation and power loss.