Question 20 (3 points) why is the moon visible? question 20 options: it is on fire. it reflects sunlight. earth lights it up. it gives off light. question 21 (3 points) what planet do scientists believe prevented the asteroids in the asteroid belt from forming a planet? question 21 options: jupiter neptune mars earth question 22 (3 points) which of the following is greater, the moon's period of rotation or its period of revolution? question 22 options: the moon's rotational period they are equal. the moon's revolution period around earth neither are known. question 23 (3 points) what condition is necessary for a lunar eclipse to occur? question 23 options: the sun is in the moon's shadow. the moon is in earth's shadow. the moon is in the sun's shadow. earth is in the moon's shadow. question 24 (3 points) what is a difference between a total solar and a total lunar eclipse? question 24 options: a solar eclipse happens once every 28 days. a lunar eclipse happens only during a full moon. in a solar eclipse, the sun moves between earth and the moon. in a lunar eclipse, the moon moves between the sun and earth. in a solar eclipse, it is earth that is caught in the umbra of the moon. in a lunar eclipse, it is the moon that is caught in the umbra of earth. a solar eclipse can be viewed anywhere on earth. a lunar eclipse can only be seen from the side of earth facing the moon. question 25 (3 points) which manned space mission visited the moon several times? question 25 options: voyager 1 apollo mercury gemini

20. Answer is "it reflects sunlight".

The moon is not a star as sun. Hence, moon can't produce light by itself. The only reason that we can see the moon is it reflects the sunlight. According to the distance from the sun to the moon, the light reflection can be varied.

21. Answer is "Jupiter".

Asteroid belt is a region which is located between Mars and Jupiter and consists of asteroids and minor planets. This asteroid belt has the 4% as the mass of our moon. Due to the Jupiter's strong gravity, it is prevented a forming of new planet by this asteroid belt.

22. Answer is "they are equal".

The period of revolution is the time which is taken by a mass to go completely one round around another mass. For moon, the period of revolution is 27 days.
The period of rotation is the time taken by a mass to complete one round around its own axis. It is about 27 days for moon. 

23. Answer is "The moon is in Earth's shadow".

Lunar eclipse happens when Sun, Earth and moon are directly aligned each other and Earth is located in between the Sun and the moon. Then the moon is covered by the Earth's shadow.

24. Answer is "In a solar eclipse, it is Earth that is caught in the umbra of the moon. In a lunar eclipse, it is the moon that is caught in the umbra of Earth".

In total lunar eclipse, Earth is located between Sun and the moon and they are directly aligned to each other. The moon is totally covered with the Earth's shadow.
Total solar eclipse can be seen when the moon is located between sun and Earth by completely covering the sun. 

25. According to the given choices, we can get "Apollo" as the answer.

Apollo 8 is the first manned mission to the moon. From that there were several manned mission including first manned landing on the moon. The Apollo program was conducted by USA.

i just got this problem. it's 90.3

it is the most commonly accepted one