Which of the following is a correct set of homologous organs?
(a) Forelimbs of frog, bird and lizard
(b) Spine of cactus and thorn of bougainvillea
(c) Wings of bat and wings of butterfly
(d) Wings of a bird and wings of a bat
Homologous organs are the organs that have a similar internal structure (similar origin). Forelimbs of a frog, bird and lizard are homologous organs.
Hence, the correct answer is option (a).