In humans, the pelvis and femur, or thigh bone, are involved in walking. in whales, the pelvis and femur shown in figure 16–1 are
a. examples of fossils.
b. vestigial structures.
c. acquired traits.
d. examples of natural variation.

The correct answer is

B. vestigial structures

The correct answer is-

C. acquired traits.  

Acquired trait is and non heritable trait, which is developed by organisms when they interact with environment that is due to environmental influences.

Pelvic bones of whales have been evolved to assist the marine mammals like whale in their reproduction that is to perform better during sex.

Whales possess small pelvic bones as compared to the size of their body. But it has been discovered now that these tiny bones actually plays a significant role in the reproduction of whales.

Therefore, pelvis and femur in whales show acquired traits.