Which of the following best represents an example of infectious disease spreading via a vector?

The correct answer is A: Being bitten by an infected mosquito. This is an example of infectious disease spreading via a vector because mosquitoes can act as carriers for diseases such as malaria, dengue fever, and Zika virus. Mosquitoes become infected by feeding on an infected host and then transmit the pathogen to a new host through their bites. This mode of transmission is known as vector-borne transmission. Choices B, C, and D do not involve a vector in the transmission of the disease. Choice B involves direct contact between individuals, not through a vector. Choice C describes vertical transmission (mother to infant) and not vector transmission. Choice D involves transmission through a fomite (shared glass) and not a vector.