Scientists have observed that pythons have vestigial leg bones. they have also observed that snakes in general have more dna sequences in common with four-legged geckos than they do with legless eels. what do these two observations have in common?
answer
they both suggest that geckos evolved from snakes.
they both suggest that pythons are more primitive than other snakes.
they both suggest that snakes evolved from an ancestor with legs.
they both suggest that snakes evolved from geckos.

The answer is They both suggest that snakes evolved from an ancestor with legs.

The second choice is not correct since we have no information about pythons and other snakes. We only have the relationship between geckos, snakes and legless eels. So, it is said that snakes in general have more DNA sequences in common with four-legged geckos than they do with legless eels. This means that snakes are closer to geckos than the legless eels. We cannot conclude from this information which evolved from which, but we can say that snakes evolved from an ancestor with legs.
In different case, if the snakes had more DNA sequence in common with legless eels, we would conclude that the snakes evolved from an ancestor without legs.

Dthrough a slow process