I think no.4 because they both have similiar basic structure but they have different functions So they both are analogous organs.

Homologous and Analogous Organs in Animals

Homologous Organs:

Homologous organs are those organs that have similar structural design and origin but have different functions. These organs suggest that the organisms with these organs have a common ancestor. For example:

1. Wing of a bird and forelimb of a horse -homologous organs.

The wings of birds and the forelimbs of horses have a similar structure and origin, but they perform different functions. The forelimbs of horses are designed for running, while the wings of birds are designed for flying. Both structures have a similar pattern of bones, suggesting that they have evolved from a common ancestor.

3. Wing of bird and wing of a butterfly -homologous organs.

The wings of birds and butterflies have a similar structure and origin but perform different functions. The wings of birds are designed for flying, while the wings of butterflies are designed for gliding. Both structures have a similar pattern of veins and muscles, suggesting that they have evolved from a common ancestor.

Analogous Organs:

Analogous organs are those organs that have different structure and origin but have similar functions. These organs suggest that the organisms with these organs have evolved separately to adapt to similar environments. For example:

2. Wing of a bat and forelimb of a squirrel-Analogous organs.

The wings of bats and the forelimbs of squirrels have different structures and origins, but they perform similar functions. The wings of bats are designed for flying, while the forelimbs of squirrels are designed for climbing trees. Both structures have similar adaptations to their environment, suggesting that they have evolved separately to adapt to similar environments.

4. Fin of a fish and wing of a bird -analogous organs.

The fins of fish and the wings of birds have different structures and origins but perform similar functions. The fins of fish are designed for swimming, while the wings of birds are designed for flying. Both structures have similar adaptations to their environment, suggesting that they have evolved separately to adapt to similar environments.

Conclusion:

Therefore, it is important to differentiate between homologous and analogous organs in animals as they provide evidence for evolution and adaptation. Homologous organs suggest that organisms with these organs have a common ancestor, while analogous organs suggest that organisms with these organs have adapted to similar environments.