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
Viruses are not the only submicroscopic bodies capable of causing disorders within cells.
Sub-viral particles are infectious agents that bear a resemblance to viruses in structure and composition. But they are notably smaller and simpler than viruses but lack either nucleic acid or protein and are thus not viruses. (Thus they may be proteins beyond nucleic acids or only nucleic acids beyond protein coat /capsid.)