Final answer:
The correct answer is C. Solstices mark the longest and shortest days of the year due to the Earth's tilt, while equinoxes mark the days when daylight and darkness are nearly equal because the sun is directly above the equator.
Step-by-step explanation:
The difference between an equinox and a solstice in terms of celestial events is significant. Solstices mark the longest and shortest days of the year, with the summer solstice having the most daylight and the winter solstice having the least. This occurs because the tilt of the Earth's axis causes the Sun to appear at its highest or lowest point in the sky during these times.
On the other hand, equinoxes occur when the tilt of the Earth's axis is neither away from nor towards the Sun, resulting in days with nearly equal daylight and darkness. This happens approximately on March 21 and September 21 when the Sun is directly above the Earth's equator. Thus, every place on Earth experiences about 12 hours of daylight and 12 hours of night.
Therefore, the correct answer is: C. Solstices mark the longest and shortest days of the year, while equinoxes mark days with nearly equal daylight and darkness.