I want to know the answer to the following question:
What is the possible cause of the upper Cretaceous extinction event ?
All the background I'm provided with is that "The upper (Cretaceous) boundary is set at the Cretaceous–Tertiary (KT) extinction event (now more accurately called the Cretaceous–Paleogene (or K–Pg) extinction event), which may have been caused by the impactor that created Chicxulub Crater on the Yucatán Peninsula.". Is that enough to answer the question?
Answer: yes