The correct answer would be number 3 which is Nephron :)
Heat stroke is the most severe form of hyperthermia.
By breathing in air when close to an infected person who is exhaling small droplets and particles that contain the virus; Having these droplets and particles land on the eyes, nose, or mouth: Or touching the eyes, nose, and mouth with hands that have the virus on them.
Basically any contact with a human could bare the risk of catching the virus.