The most compelling evidence we have for a large asteroid striking the Earth and causing mass extinction, particularly the event that led to the extinction of the dinosaurs about 66 million years ago, includes:
B. Iridium found only in asteroid is found worldwide in the same rock layer.
This evidence refers to the discovery of elevated levels of iridium in a specific geological layer known as the Cretaceous-Paleogene (K-Pg) boundary. Iridium is rare on Earth's surface but more abundant in asteroids, supporting the hypothesis that a cosmic impact occurred. This is a key piece of evidence linking the asteroid impact to global extinction events.
A. Fossil evidence found in rocks can also support the hypothesis, showing the dramatic changes in species before and after the impact. However, it is not as direct as the iridium layer.
C. Carbon dating shown in rock layers is more commonly used for dating organic materials and is not directly related to the asteroid impact theory.
In conclusion, the best answer to your question is B.