The term "most infectious disease" can be understood in different ways, depending on the context. If you're asking which disease has the highest potential for transmission, then the answer would typically be respiratory infections like the common cold or influenza (cough and cold).
However, if you're asking about a disease with a high potential for transmission through specific routes (such as blood or sexual contact), then hepatitis B and HIV/AIDS are of concern.
So, thew correct option is (C): Cough and Cold