What is the length of one degree of longitude at 28°n latitude?

69 miles (111 kilometers)

Explanation:

Each degree of latitude on the surface of the earth is about 68 miles away from each other this is caused due to the axial tilt and elliptical shape or bulge of the planet. From 68.703 miles (110.567 km) at the equator to 69.407 (111.699 km) at the poles. Since the longitude varies from equator to poles the poles see most of the variations. For calculating the degree of longitudes first convert latitude into decimal ~ 37.26  then convert your decimal into radians ~ 0.650. Take out the cosine in radians ~ 0.795 Thus one degree of Longitude = ~0.795 * 69.17 = ~ 55.05 miles .

I'm pretty sure it's c. extremely gradual but not 100% sure though.

Answer were lower;