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.
