What is the author's purpose in mentioning "Boat designers" in a discussion of the amount of energy used in swimming? A. To illustrate the point that large animals are not efficient swimmers because they produce very large bow waves B. To make a comparison between the type of drag produced by the bow wave and the type produced by an animal's weight C. To suggest that boat designers could design better boats if they studied locomotion in animals D. To apply a principle used in boat design to further illustrate why surface swimming is inefficient