Which unit is used to represent the average distance between earth and sun and distances within the solar system?
(A) Light year
(B) Astronomical units
(C) Parsec
(D) Angstrom

Hint The light year is the distance which is travelled by light in one Julian year. It is a unit of length.
Astronomical unit is also a unit of length which is used for measuring distance in the solar system.
The parsec is a unit of length which is used to measure large distances. It is used to measure distances outside the solar system.
The Angstrom unit is a unit of length which is equal to ${10^{ - 10}}m.$

Complete step by step answer:
Light year is used to measure length which is equal to about 9.46 trillion kilometres. Generally, light years are used to express distances to stars.
Astronomical unit measures about 150 million kilometres and is the distance between earth and sun. It is used to measure distances within the solar system. The symbol for the astronomical unit is AU. This unit also measures the mean distance between earth and sun.
The Parsec is a unit of length which measures the large distances outside the solar system. It is approximately 31 trillion kilometres approximately. It is obtained by the use of parallax and trigonometry.
Angstrom is the metric unit of length which is equal to ${10^{ - 10}}m.$ It is ten-billionth of metre, 0.1 nanometre and 100 picometres. It is mostly used in crystallography, solid state physics and chemistry..
Therefore, the Astronomical unit is used to represent the mean distance between earth and sun and distances within the solar system. Hence, option (B) is the correct answer.

Note Astronomical unit is about 93 million miles or 150 million kilometres.
Mean distance from sun to each planet in astronomical unit-
Mercury = 0.387 AU
Venus = 0.723 AU
Earth = 1.00 AU
Mars = 1.52 AU
Jupiter = 5.2 AU
Saturn = 9.58 AU
Uranus = 19.2 AU
Neptune = 30.04 AU