Definition: You are given a question on high school geography. 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: Early settlements and high population density along coastlines and rivers are best attributed to which of the following?
(A)Mediterranean climate (B)Limited forest cover (C)Growth of manufacturing (D)Access to trade routes

D