Look at this character table. rattlesnakes (like turtles) are reptiles, yet they do not have four limbs. in fact, they have no apparent limbs.

The fact that the rattlesnakes had no apparent limbs shows the kind of events that occurred during their evolutionary period. Snakes originated from reptiles, which had four limbs, but as time goes on during evolution,  the limbs in the rattlesnakes becomes highly reduced and eventually they lose this feature that is found in other reptiles. 

A. mitochondrion b. nucleus

Your answer is going to be a. i know my biology