1. Nephridia are the excretory organs that are most commonly seen in earthworms.
2. Gizzard is present in alimentary canal of some insects, which helps in crushing food particles.
3. Flame cells are the excretory organs of platyhelminthes.
4. Malpighian tubules constitute the excretory organs of cockroach and other insects.
So, the correct option is 'Malphigian Tubules'.