Well, a homologous structure is a bone or something else that is present in many different species that could point to a common ancestor. Since you do not have the examples in your question I will just give you some and hope that it helps you:
The arm of a human, the wing of a bird or a bat, the leg of a dog and the flipper of a dolphin or whale.
I hope this helped! Let me know if it did not!
I hope you have a fantastical day!!XD
