The correct answer is: A. summer and winter solstices
The ecliptic is the apparent path of the Sun across the sky as seen from Earth. The celestial equator is an imaginary line in the sky that is directly above the Earth’s equator. The summer and winter solstices are the two points on the ecliptic that are farthest north and south of the celestial equator.
The summer solstice occurs when the Sun is at its highest point in the sky in the Northern Hemisphere. This happens on or around June 21st. The winter solstice occurs when the Sun is at its lowest point in the sky in the Northern Hemisphere. This happens on or around December 21st.
The autumnal equinox occurs when the Sun crosses the celestial equator from south to north. This happens on or around September 22nd. The vernal equinox occurs when the Sun crosses the celestial equator from north to south. This happens on or around March 20th.
The north celestial pole and south celestial pole are the two points in the sky directly above the Earth’s north and south poles, respectively. These points are not on the ecliptic.