Answer:
(a) bat wing and human hand.
Explanation:
Homologous structures are structures with the same embryonic origin but are modified to perform different functions.
Both the bat wing and the human hand are pentadactyl (five digit) limb structure though they perform different functions.Their bat wing and human hand limb contain of three parts;the humerus ,the radius and ulna,a hand made up of carpals ,metacarpals and phalanges.
This clearly indicates that they share a common ancestry but due to divergent evolution they are modified to perform different functions hence referred to homologous structures.