The correct answer is c. The 50W bulb has half the resistance of the 100W bulb. This is because the power consumed by a light bulb is given by P = V^2/R, where P is power, V is voltage, and R is resistance. Since both bulbs are connected to the same 110 V source, the power consumed by the 50W bulb must be half of the power consumed by the 100W bulb. Solving for R, we get R = V^2/P. Since V and P are constant for both bulbs, the resistance of the 50W bulb must be half of the resistance of the 100W bulb.