3. Now wait until the planet is at the summer solstice (to the far left). Here the sunlight arrives perpendicular to the surface. (Note that the fact that the sunlight can be perpendicular to the surface here and parallel to the surface at the winter solstice with the same tilt of the axis is an unfortunate coincidence related to the latitude of the observer. For any other latitude, this would not happen.)

When the sunlight strikes perpendicular to the surface, what percentage of the light arrives perpendicular to the surface?
0%
50%
75%
100%