How do topographic maps compare in their representation of continental and ocean-floor topography? A. Both continental and ocean-floor topography are measured relative to the Earth's center. B. Both continental and ocean-floor topography are measured relative to sea level. C. Continental topography is measured relative to sea level, while ocean-floor topography is measured relative to the Earth's center. D. Ocean-floor topography is measured relative to sea level, while continental topography is measured relative to the Earth's center.