Answer the following question given this paragraph: 

Vertebrates have an adaptive immune system. The immune system is the organ system that defends the body from pathogens and other causes of disease. Being adaptive means that the immune system can learn to recognize specific pathogens. Then it can produce tailor-made chemicals called antibodies to attack them. This allows the immune system to launch a rapid attack whenever the pathogens invade the body again.


Q: Which organ system defends the body from pathogens and other causes of disease?

 Choices:

- digestion system

- nervous system

- respiratory system

- immune system

A:
immune system
