Three identical lightbulbs A, B, and C are arranged so that bulbs A and B are connected in parallel with each other, and this parallel pair is connected in series with bulb C to an ideal battery. All bulbs are glowing steadily. If bulb B suddenly burns out (its filament breaks, creating an open circuit in that branch), what happens to the brightness of bulbs A and C?
a) Bulb A remains at the same brightness, and bulb C becomes dimmer
b) Both bulbs A and C become dimmer
c) Bulb A becomes brighter, and bulb C becomes dimmer
d) Bulb A becomes dimmer, and bulb C becomes brighter