Which feature of four different marine fossils makes the fossil organism most similar to the present-day organism with four limbs?

I found the rest of the exercise on the internet and these are the options.
"-Undifferentiated vertebrae throughout the body.
-One neck vertebra allowing up and down movement.
-Many neck vertebrae that allow for greater mobility.
-Two neck vertebrae allowing up and down and sideways movement."

The correct answer would be the third. - "Many neck vertebrae that allow for greater mobility." The present-day organism with four limbs has a neck with several vertebrae that allow movements of rotation (mostly because of only two vertebrae at the top of the neck), and side way movements, as well as back and forth movements.

What? i don’t understand