Question

Which of the following is not a unit of time?
(A) Parsec
(B) Light year
(C ) Micron
(D) Second

Answer 1

Hint: Parsec and light year are not practical units of time. They are used to measure large distances. That is, it is used to measure distances like between the sun and earth or other celestial bodies. Parsec is also a unit of distance, which is used to measure astronomical distances. So the units of time are second.

Complete step-by-step solution
The common units of time are second. The SI unit of time is second and is denoted by the letter ‘s’.
Parsec is a unit of distance. A light-year is also used to measure distances. It is used to measure distances between the sun and earth or other celestial bodies.
Parsec is also a unit of distance, which is used to measure astronomical distances. Thus parsec can be defined as a distance used to measure in astronomy which is numerically equal to 3.26 light-years.
A light-year is also an astronomical distance which the distance traveled by light in a year.
Whereas, micrometer or micron is a unit used to measure length. That is, usually used to measure the thickness of some materials.
Thus option (A), (B) and (C ) is correct.

Note: Parsec is also a unit of distance which is used to measure astronomical distances. Thus parsec can be defined as a distance used to measure in astronomy which is numerically equal to 3.26 light-years. A light-year is also an astronomical distance which the distance traveled by light in a year. Whereas, micrometer or micron is a unit used to measure length. That is, usually used to measure the thickness of some materials.