A person who has a weakened immune system may not be able to fight against infection because pathogens may enter the body and cause illness.
phagocytes may enter the body and cause illness.
normal cells crowd out unhealthy cells.
antibodies production is increased.

answer axon terminal,synaptic cleft; and motor end plate;

option d : from a warmer substance to a cooler substance

according to second law of thermodynamic, heat flows from higher to lower temperature region. heat is the transfer of energy from an object at higher temperature to an object at a lower temperature. so energy flows from warmer to colder objects.