The main function of the immune system is defending against infectious agents. Here's why:
1. **Defending against infectious agents:** The immune system is responsible for protecting the body from harmful invaders like bacteria, viruses, fungi, and parasites. It does so by identifying and attacking these pathogens to prevent infections and diseases.
Other functions listed, like body temperature regulation, hormone production, and blood clotting, are important processes in the body but are not the primary function of the immune system. Temperature regulation helps maintain the body's internal environment, hormone production controls various body functions, and blood clotting is essential for wound healing and preventing excessive bleeding. However, these functions are not directly related to defending against infectious agents like the immune system is.
