a) bulb "C" will be more brighter
Because we know that R is directly proportional to l/A .
Since the thickness of the filament are the same, then the area of cross section i.e. A will be equal.
But the lengths are different.
We can say that,
R is directly proportional to l
Hence, the filament having the maximum length will glow brightly
Therefore the answer to this question is "c"
