Final answer:
The frills on Ceratopsids served various roles including thermoregulation, muscle attachment, and display. The exoskeleton and fusiform shape are distinct biological features providing protection, muscle attachment, and streamlined movement for different species.
Step-by-step explanation:
The frills on Ceratopsids, a group of herbivorous dinosaurs, functioned for multiple purposes. These include: thermoregulation, acting as sites of attachment for jaw-moving muscles, and possibly display purposes, such as species recognition or sexual selection. Therefore, the correct answer is d. all of the above.
Regarding other biological terms, an exoskeleton is a rigid external covering for the body in some invertebrate animals, particularly arthropods, that provides both protection and a surface for muscle attachment. Organisms such as dolphins are known to have a fusiform body shape, which is streamlined to reduce water resistance and allow swift movement through their aquatic environment. This body form is less common in terrestrial animals. Endothermy is a characteristic of certain animals, including mammals which have evolved ways to maintain a stable internal body temperature. These biological functions and features contribute to the wide variety of body forms and functions across different species.