Final answer:
A horizontal loop on a modern roller coaster would appear as a teardrop shape from a top view, which helps to manage centripetal acceleration for the passengers.
Step-by-step explanation:
From a top view, a horizontal loop on a roller coaster would look like a circle if it maintained a constant radius throughout the loop. However, modern roller coasters typically do not have loops that are perfect circles when viewed from above. Instead, they use teardrop-shaped loops, as explained in the provided information. This design helps to manage the centripetal acceleration experienced by riders. Thus, from a top view, a horizontal loop on a modern roller coaster would appear as a teardrop shape, matching option C in the choice of answers provided by the student.