Which statement is true?
the earth's moon is thought to have formed when a mars-sized planet collided with earth during its final stages of planetary accretion.
without the earth's moon, life on earth would not be possible.
the earth's moon is the smallest moon relative to its host planet.
the earth's moon is the same size as the earth.

The correct answer should be
The earth's moon is thought to have formed when a Mars-sized planet collided with Earth during its final stages of planetary accretion.

That's because life would be harder but it would not be impossible to live without the moon, and there are smaller ones relative to the host planet, especially around Pluto. It's not the same size as earth.