Which of the following causes communicable diseases?

Communicable diseases are illnesses that can be transmitted from one person to another, often caused by infectious agents. The correct answer, which includes bacteria, viruses, parasites, and fungi, accurately reflects the different types of pathogens that can lead to these diseases.

Bacteria and viruses are well-known causes of communicable diseases, such as influenza, tuberculosis, and strep throat. However, parasites can also be responsible for infections like malaria and giardiasis, while fungi can lead to conditions such as athlete's foot and ringworm. Since the question encompasses all categories of infectious agents that can transmit communicable diseases, the inclusion of both bacteria and viruses as well as parasites and fungi supports the conclusion that both A and B are correct. Therefore, the answer that combines all these elements is the most comprehensive and accurate.