Which statement is true for observers located on the equator?

For observers located on the equator, the statement that the azimuth of sunrise and sunset is constant is particularly relevant. At the equator, the sun rises in the east and sets in the west, and this does not vary throughout the year as it does at higher latitudes.

Moreover, the duration of the day is relatively constant, remaining close to 12 hours of daylight and 12 hours of night throughout the year. The sun does cross the observer’s meridian daily, reaching its zenith point along the equator at noon during equinoxes.

These facts collectively lead to the conclusion that none of the statements regarding the seasonal variation in day length or the sun's azimuth across the horizon hold true for an observer at this specific latitude. Therefore, the answer indicating that none of the options provided are valid is the correct choice.