答案：C

解析：

Choice C is the best answer. The passage states that predatory shark activity has been affecting the southern sea otter population in the south subsets of the coastal range. The graph shows that in the south region, there were approximately 400 southern sea otters in 2003 and roughly 700 southern sea otters in 2009. Taken together, this information suggests that predatory shark activity was more of a threat to sea otters—and decreased their population more—in 2003 than in 2009.