Which of the Following Best Explains How a Population's Average

Which of the following best explains how a population's average height can increase from generation to generation in an environment where being tall does NOT provide a selective advantage?

A) cultural reasons, such as stretching exercises
B) a better diet becomes available to children
C) in reality this cannot happen
D) genetic drifting mutations occur
E) taller people are better able to see (and thus escape from) predators