Which of following is most dangerous environment hazard to mankind? 

Nuclear winter is the climatic effects of nuclear war. It is the damaging effects of the light, heat, blast, and radiation caused by a nuclear explosion. Smoke from the fires started by nuclear weapons will be heated by the sun. They will rise in the upper stratosphere, and spread globally resulting in thick black clouds that could block out fraction of the sun?s light for a period as long as several weeks that would cause the surface temperatures would plunge for a few weeks. Hence semidarkness, killing frosts, and subfreezing temperatures, combined with high doses of radiation would stop plant photosynthesis. This will destroy earth?s vegetation and animal life. Hence a nuclear war could thus reduce human population to a very low number. Thus the correct answer is option C.