Question

what does the immune system protect the body against?
changes of the internal body temperature
changes in the temperature of environment
changes caused by harmful pathogens
changes in the ph of the blood

Explanation:

The immune system's main function is to defend the body against harmful microorganisms (pathogens) like bacteria, viruses, etc. Internal body temperature regulation is by thermoregulatory mechanisms, environmental temperature changes are adapted to by physiological/behavioral responses, and blood pH is maintained by buffer systems, not the immune system. So the correct option is about changes from harmful pathogens.

Answer:

C. changes caused by harmful pathogens (assuming the third option is labeled C; if the original labels were different, adjust the identifier but the text is "changes caused by harmful pathogens")