1. When the Moon on its path, moves between the Sun and the Earth, will block the sunlight, but since it is smaller, it will block the central part of the sun while the sun's ring will be visible, it is the solar eclipse.
The answer is B.
2. There are two types of Solar System, an outdated geocentric model with the claim that the Earth is in the center, and all the planets together with the Sun revolve around it, and the heliocentric with the Sun in the center as all the planets revolve around the Sun.
The answer is C.
3. The astronomical unit is the unit for measuring the length in the cosmos and is about 150 million miles. It represents the average distance from Earth to the Sun, because Earth changes its distance to the Sun on its orbit during the year due to the orbit shape. This distance from Earth to the Sun varies from its maximum - aphelion, to its minimum - perihelion, so that the average value is used.
The answer is D.
