In humans, the pelvis and femur, or thigh bone, are involved in walking. In whales, the pelvis and femur shown i

The question is incomplete. The complete question is as following:

In humans, the pelvis and the femur, or thighbone, are involved in walking. In whales, the pelvis and femur shown in this figure represent...

vestigial structures

Explanation:

A "vestigial structure" or "vestigial organ" are defined as the organs that no longer have any function in the organisms' body but had an important role in past.

Pelvis and femur are thigh bones in humans which helps them in walking but in whale's pelvis and femur are considered as vestigial structures.

The pelvis and femur in whales, are the inherited structure from ancestors and shows evidence for evolution on the basis of natural selection.

Hence, the correct answer is vestigial structures.

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.