Which body system produces proteins that fight infections
the digestive system
the immune system
the muscular system
the circulatory system

Ans.

The body system that functions to fight infections and provides immunity to the body is immune system. Various protein molecules are synthesized and released by immune system that fight with disease-causing pathogens. An example of immune proteins is antibodies, which are responsible for identification and neutralization of foreign pathogens.

Thus, the correct answer is 'option). the immune system.'

Layer A: inner core

Explanation:

The solid, inner core (Layer A) is comprised mainly of iron and nickel and is scorching hot. The outer core (Layer B) does have iron and nickel as well, but it's in its liquid form. The lower mantle (Layer C) consists of iron-rich perovskite, which is a ferromagnesian silicate mineral. The upper mantle (Layer D) is made of olivine, pyroxene, calcium oxide, and aluminum oxide.