How can these forelimbs explain how life changes over time?

Option D

Explanation:

All these images are of homologous structure in different species. They are called homologous as their skeletal elements have similarity which indicates their connection to a common ancestor. They are structurally similar but look different and also have different function.  

These homologous structures depicts the changes that have occurred in the course of evolution of these organism in different geographic entities and under different circumstances  (even after coming from the same ancestors) due to which similar body organs have adapted themselves to a different function or they might have become function-less.  

For example - Tails in monkey, rats and mammals are structurally same organs but have different functions in different species. However, in case of humans tails have become function-less.  

Hence, option D is correct

of those who start drinking before they're 15 will develop alcohol dependence