What is the maximum speed limit on Florida's interstate highways?

Answer: C — 70 mph

Florida's interstate highways have a maximum speed limit of 70 mph. This option is the only one that falls within the average speed limit range for most interstate highways in the United States, which is between 65 and 75 mph. Option A is too low and would result in slower traffic flow, while options B and D are too high and pose potential safety hazards. Therefore, option C is the most reasonable and correct answer.