Forelimbs of cat used in walking; flippers of whale used in swimming and forelimbs of bats used in flying are an example of:   

Organs which have a common fundamental anatomical plan and similar embryonic origin whatever varied functions they may perform are regarded as homologous organs. For examples the flippers of a whale, a bats wing, fore-limb of a horse, a bird’s wing and forelimbs of human are structurally as well as functionally different.