An Anthropologist Wants to Compare the Average Lifespans of the Current

An anthropologist wants to compare the average lifespans of the current residents of a village in Uganda to that of those who resided there 100 years ago. Five residents who died this year are randomly selected to be compared to five residents who died 100 years ago. Although the difference in average lifespans is 16.4 years, the results are not statistically significant (P-value = 0.2169) . The most likely explanation is

A) that it is unlikely that the measurements from 100 years ago are accurate.
B) that 16.4 years isn't really a long time when considering an entire lifetime.
C) that the sample size is small, so variability makes large differences hard to detect.
D) that the calculation was in error.