Question

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.

Explanation:

To solve this, we analyze each option:

• Option 1: Pathogens (disease - causing agents) can enter a weakened immune system and cause illness as the immune system can't fight them off. This makes sense.
• Option 2: Phagocytes are part of the immune system that fight pathogens, not cause illness. Eliminate.
• Option 3: Normal cells crowding out unhealthy cells would be a sign of a healthy immune response, not a weakened one. Eliminate.
• Option 4: A weakened immune system would have decreased, not increased, antibody production. Eliminate.

Answer:

A. pathogens may enter the body and cause illness.