Answer the following question given this paragraph: 

Immune system organs include bone marrow, the thymus gland, the spleen, and the tonsils. Each organ has a different job in the immune system.


Q: Bone marrow, the thymus gland, the spleen, and the tonsils are organs in what body system?

 Choices:

- skeletal system

- nervous system

- reproductive system

- immune system

A:
immune system
