Which of the following statements best defines autoimmune diseases? 1. diseases in which the immune system is not able to produce antibodies 2. diseases in which the immune cells’ attacks do not affect the foreign agent 3. diseases in which the immune system fails to recognize the foreign agents that have entered the body 4. diseases in which the immune system attacks the body’s own tissues, falsely identifying them as invaders

4. diseases in which the immune system attacks the body’s own tissues, FALSEly identifying them as invaders

Explanation:

Components of the immune system are able to distinguish between the self and invading substances/proteins and exert their responses towards the invading foreign substances only. An autoimmune disease occurs when the immune system is not able to make such a distinction between the self and foreign substances and attack the body's own tissues/cell/proteins or other molecules.

For example, rheumatoid arthritis is an autoimmune disorder in which the immune system attacks the synovial membranes of the joints of the body.

4. diseases in which the immune system attacks the body’s own tissues, FALSELY identifying them as invaders

Explanation:

b. the carbon cycle ensures living things have a source of hydrogen

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