Question

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what is the immune system?
a network of blood vessels that transport oxygen throughout the body.
a system of muscles that helps the body move.
a group of organs responsible for breaking down food and absorbing nutrients.
a complex network of cells, tissues, and organs that work together to protect the body from pathogens.
a collection of cells that produce and secrete hormones.

Explanation:

The immune system is a complex network. It consists of cells, tissues, and organs. Its main function is to protect the body. It does so by defending against pathogens (such as bacteria, viruses, etc.).

• The first option describes the circulatory system (blood vessels transporting oxygen).
• The second option refers to the muscular system (muscles for movement).
• The third option is about the digestive system (breaking down food, absorbing nutrients).
• The fifth option pertains to the endocrine system (cells producing and secreting hormones).

Answer:

A complex network of cells, tissues, and organs that work together to protect the body from pathogens.