The most common carrier of communicable diseases is __________.

The most common carrier of communicable disease is the housefly. Houseflies are considered the primary carriers because they live in unhygienic areas like garbage, sewage, and animal waste. When they come into contact with food or surfaces, they transfer harmful microorganisms, including bacteria, viruses, and parasites, which can cause diseases such as diarrhea, cholera, and typhoid.

The most common carrier of communicable disease is not ants, spiders, or dragonflies because these insects do not have the same habits of visiting and contaminating food or human living spaces as houseflies do. Houseflies are unique in their ability to spread illnesses because their hairy legs and sticky saliva allow them to carry germs effectively.

In conclusion, the most common carrier of communicable disease is undoubtedly the housefly due to its unhygienic living habits and contact with contaminated substances.