The correct answer is D) aphelion. The Sun reaches its maximum declination north when it is at the aphelion, which is the point in the Earth's orbit when the Earth is farthest from the Sun. At this point, the Sun's apparent position in the sky is at its northernmost point, resulting in the longest day and shortest night in the Northern Hemisphere (summer solstice). The other options are incorrect because: A) the autumnal equinox is when the Sun crosses the celestial equator heading south, B) perihelion is the point when the Earth is closest to the Sun, and C) the first point of Aries is the vernal equinox, not the position of the Sun at its maximum declination north.