The pelvic bones of whales are located in the equivalent position to the hip bones of land mammals, though they are not attached to the rest of the skeleton. These bones have long been thought of as vestigial structures leftover from the process of evolutionary change. Scientists researched the relationship between the size of whale pelvic bones and the size of whale testes. The graphs show some of the results of the study.
Which of the following statements relating to whale pelvic bones are correct?
I. Whale pelvic bones are homologous to the pelvic bones of land mammals.
II. There is no relationship between the body size of a whale, as represented by rib size, and the size of a whale's testes.
III. The pelvic bones of whales are vestigial structures with no function.
IV. The pelvic bones of whales are not vestigial but are involved in reproduction.