Final answer:
To view the entire celestial sphere at night, one must observe the sky at different times of the year and from various latitudes, as the Earth's tilt, rotation, and orbit impact the visibility of celestial objects.
Step-by-step explanation:
In Astronomy, to see all of the celestial sphere at night, you would need to observe at different times of the year and from different latitudes. This is because the Earth’s tilt and orbit around the Sun affect which parts of the celestial sphere are visible at different times. Additionally, your latitude affects the angle at which you view the celestial poles and the celestial equator. For instance:
If you are at the equator, the celestial equator will pass through your zenith, and stars will rise and set perpendicularly to the horizon. Over the course of a year, you would see different stars, allowing for the visibility of all stars from this latitude.
At the North Pole, stars circle the zenith and never rise or set, and only the northern half of the celestial sphere is visible. Here, during the summer months, the Sun barely sets, making it difficult to observe stars due to the prolonged daylight.
The correct answer to the question is D. A & B, observe at different times of the year, and observe from different latitudes.