Definition: You are given a question on prehistory. You are also given 4 answer options (associated with "A", "B", "C", "D"), out of which only one is correct. You need to answer the question by selecting the correct option. You should only answer with the choice letter, not the whole answer.
Input: What may have caused the Ancestral Puebloans to abandon Mesa Verde?
(A)the population outstripped the productive capacity of the environment (B)drought (C)a new religion attracted them to the south (D)all of the above

D