The Mass Extinction at the End of the Cretaceous Period

The mass extinction at the end of the Cretaceous period about 65 mya is believed to have been caused by a massive comet or asteroid smashing into what is now known as the Yucatan peninsula in the Gulf of Mexico.The debris arising from this impact would have blocked the Sun's rays from reaching the Earth.How would this cause a mass extinction?

A) With no sunlight,the plants would not be able to photosynthesize food for themselves,and they would die.Any animals that fed on those plants would also die,and any animals that would have eaten those animals would also now starve to death.This chain reaction would continue up the food chain.
B) A giant fireball would have spontaneously incinerated every living thing,and the evolution of life on Earth would have started completely fresh.
C) A massive wave spread out from the epicenter of the impact and drowned all of the terrestrial life on Earth.Evolution of all life on land started over after that event.
D) All of the terrestrial plants and animals choked to death on the debris cloud.