65 million years ago there was a mass extinction that is best known for killing the dinosaurs. There was also a large deposit of dust that contained substances only found in asteroids. What most likely killed off the dinosaurs?

The asteroid-only substances in the dust suggest that a large asteroid struck Earth. The impact would have thrown dust and debris into the atmosphere, blocking sunlight and disrupting plants and food chains. This makes “An asteroid impact caused the Sun to be blocked” the best answer; the dinosaurs were not all directly crushed by the asteroid.

AI-written and checked against the verified answer.