Pandas live for about 20 or so years
Answer : Option C) vestigial structures.
Explanation : In the example of whales which is displaying the remnants of the pelvis and femur bones it seems to be the example of vestigial structures.
As vestigial structures are those anatomical feature which no longer seems to have a purpose in the current form of an organism of the given species.
It would drop you pH levels in your body prior to eating. When you eat the burger it will bring it back up, hopefully to 7 (neutral)