Final answer:
Epithelial cells that are not tightly packed together can lead to increased vulnerability to infections, due to the compromised protective barrier they usually provide.
Step-by-step explanation:
A possible negative side effect of having epithelial cells that are not tightly packed together is increased vulnerability to infections. This is because the tight junctions between the epithelial cells typically serve to prevent the entry of harmful microorganisms into the body. When these cells are not closely packed, it can compromise the protective barrier functioning of the epithelial tissue, making it easier for pathogens to penetrate and potentially cause harm to the organism.
The correct answer to the student's question is: a) Increased vulnerability to infections; harmful microorganisms can easily penetrate the body.