In the Section "Investigating Life: Evolving Backwards," What Is the Significance

In the section "Investigating Life: Evolving Backwards," what is the significance of the marine fossil snakes (highlighted in the figure) ?

A) Is an ancestor to modern-day snakes and has same anatomical organization as modern-day snakes
B) Is an outgroup unrelated to modern-day snakes
C) Has the same anatomical organization as modern-day snakes
D) Has a common ancestor to modern-day snakes,but placed in a derived group
E) Is the ancestor to modern-day snakes,but has different anatomical organization than modern-day snakes