Answer: Option D. -> when the Moon comes between the Sun and the Earth.
Answer: (d)
The eclipse of the Sun occurs when the Moon comes between Sun and the Earth. The Moon orbits the Earth once a month, and eclipses happen if it lines up exactly with the Earth and the Sun. Solar eclipses occur at New Moon when the Moon is between Earth and the Sun.
Lunar eclipses occur at Full Moon when Earth is between the Sun and the Moon. Eclipses do not take place every month because the orbits of the Moon and Earth are tilted at an angle. Most of the time, the line-up is not precise enough for an eclipse.

Answer: Option B. -> Nebulae
Answer: (b)

Answer: Option A. -> 3 only
Answer: (a)The North and South poles have either no night for around six months of the year during summer, or complete night for six months of the year during winter.This is because, during summer, the sun is basically permanently above the horizon for half of the year, due to the tilt of the earth on its axis. If the earth were positioned upright with the poles in a vertical position, then the North and South Poles would have daytime and night time separated by light and darkness, just like the rest of the planet.However, because it is tilted and rotates around the sun's energy for six months one pole or the other has to always be in the shadow.

Answer: Option D. -> Venus
Answer: (d)

Answer: Option C. -> Earth
Answer: (c)Earth is called the ‘Blue Planet’ due to the abundant water on its surface. This is because liquid water covers most of the surface of the planet. The Earth has the right mass, chemical composition, and location can support liquid water.

Answer: Option C. -> Brittle star
Answer: (c)

Answer: Option A. -> When the moon is between the sun and earth
Answer: (a)A solar eclipse occurs when the moon gets between Earth and the sun, and the moon casts a shadow over Earth. A solar eclipse can only take place at the phase of new moon, when the moon passes directly between the sun and Earth and its shadows fall upon Earth’s surface.

Answer: Option B. -> Sun shining in the polar circle for long time
Answer: (b)

Answer: Option D. -> 3 4 1 2
Answer: (d)
As Earth revolves around the Sun there are two moments each year when the Sun is exactly above the equator. These moments are called equinoxes which occur around March 20 or 21. The summer solstice occurs during the hemisphere’s summer.
This is the northern solstice in the northern hemisphere and the southern solstice in the southern hemisphere. Depending on the shift of the calendar, the summer solstice occurs sometime between June 20 and June 22 in the northern hemisphere and between December 20 and December 23 each year in the southern hemisphere.
The winter solstice (or hibernal solstice), also known as midwinter, is an astronomical phenomenon marking the day with the shortest period of daylight and the longest night of the year.
In the Northern Hemisphere this is the December solstice and in the Southern Hemisphere, this is the June solstice. It occurs on 22 September in the northern hemisphere and 20 March in the southern hemisphere. The autumnal equinox occurs on September 23.

Answer: Option C. -> 1 and 2 only
Answer: (c)The Earth completes one “rotation” every twenty four hours. A rotation is when the planet spins around once. The Earth rotates counter-clockwise; this is why the Sun “rises” in the east and “sets” in the west. Revolution is when one object completes a circular path around another object. The Earth takes 365.24 days to revolve around the Sun. This is why a year is 365 days long. During the year the Earth is angled differently towards the Sun.These changing angles provide us with different Sun intensities and therefore we get four different seasons.