Which disease is caused by droplet transmission?

Droplet transmission refers to the spread of infectious pathogens through respiratory droplets that are expelled when an infected person coughs, sneezes, or talks. Among the options given, pneumonia can result from various infectious agents, many of which are spread through droplet transmission. For example, bacterial pneumonia can be caused by Streptococcus pneumoniae, which is often spread when an infected person releases respiratory droplets into the air, allowing others to inhale the pathogens.

While measles is indeed transmitted through respiratory droplets as well, it is classified more specifically as a highly contagious viral infection, often necessitating direct exposure to an infected person. Smallpox also spreads through droplets but is no longer a concern due to its eradication. Malaria, on the other hand, is transmitted through the bite of infected mosquitoes and does not involve droplet transmission at all.

Therefore, considering the nature of pneumonia and its common modes of transmission, the understanding of droplet transmission within the context of this question showcases why pneumonia is the most fitting choice among the options mentioned.