Explanation

Gigantic clouds of dust and gas in space are called nebulae

Primarily hydrogen and helium, plus dust (silicates, carbon, ice). 

Occupying the space between stars and acting as a nursery for new stars

Explanation

The effects of the thyroid come from two iodine containing-hormones

Explanation

CNG as compared to other fuels, causes less pollution.

The reason is that it is made up of methane.

There is less carbon emission.

Explanation

The hip and knee are the largest joints in the body.

The femur is the longest bone in the human body and the shortest bone is the stapes found in the middle ear.

Explanation

Explanation

The Earth can be divided into four main layers: the solid crust on the outside, the mantle, the outer core and the inner core. Out of them, the crust is the thinnest layer of the Earth, amounting for less than 1% of our planet's volume.

Explanation

The ozone layer protects the Earth against most UVB coming from the sun.

Explanation

The color of water varies with the ambient conditions in which that water is present.

Explanation

Iodine and sodium are essential for animals and are not required by most of the plants however, iodine is found in certain marine algae.

Explanation

A lunar eclipse occurs when the Moon moves into the Earth's shadow.

This can occur only when the Sun, Earth, and Moon are exactly or very closely aligned with Earth between the other two, and only on the night of a full moon.