答案：B

解析：

Choice B is the best answer. The passage explains that the southern sea otter will no longer be considered a threatened species if the species' population index exceeds "3,090 for three consecutive years" and indicates that at the time of the survey, the three-year running average of the sea otter population was 3,054, with most of the sea otters in the central coastal range. The graph shows that a large number of southern sea otters are in the central range and that the population there has been increasing since about 2012. If the growth of the large population of southern sea otters in the central region were to continue, it is likely that the total population would increase above 3,090 and remain large enough to be removed from the threatened species list