Which one correctly describes homologous structures?

Homologous structures are those organs with different roles but similar basic anatomical characteristics.

1. Homologous organs may not be identical, but they do share a common ancestor or embryonic origin.
2. Although homologous organs share a similar anatomical structure, they are altered to serve different tasks. 
3. The arm of a human, a bat's wing, and a dolphin's flipper are three examples of homologous structures. 
4. They are regarded as homologous structures because, although having similar morphology, they serve different purposes. 
5. Humans have adjusted their arms to perform grasping and gripping tasks. A bat's wing is altered to serve as its flying mechanism. The dolphins' flippers serve as their swimming fins.

Hence, option A is the correct answer.