The correct answer is:
c.) Living within red blood cells
Step-by-step explanation:
Some protozoa have the ability to invade and live within red blood cells, which is a strategy they use to cause diseases. By residing within the host's red blood cells, these protozoa can evade the immune system and continue to multiply, leading to the development of various diseases. This strategy is employed by certain species of protozoa, such as Plasmodium, which causes malaria.