Select the option in which the two words are related in the same way as are…

Concept

This is a quantity-to-measuring-unit analogy: the first word names a physical quantity, and the second word names the standard unit conventionally used to measure that quantity.

Application

Litre is the unit used to measure Volume.

Applying the same relationship: Radian is the unit used to measure Angle.

So Angle : Radian follows the same quantity-to-unit pattern as Volume : Litre.

Why the other pairs don't match

• Pressure : Kelvin — Kelvin is the unit of temperature, not pressure; the unit for pressure is the pascal, so this pairing is mismatched.

• Second : Clock — a clock is a measuring instrument, not a unit; second is itself already a unit (of time), so pairing it with an instrument breaks the quantity-to-unit pattern.

• Liquid : Pascal — liquid is a state of matter, not a measurable quantity, and pascal is the unit of pressure rather than of liquid, so neither half of the pair matches the required relationship.

Hence, Angle : Radian is the correct match.

Additional Information

Confusion Points

• Second is also used to measure angles, as the smallest unit in the Degree-Minute-Second notation, but its SI role is as the unit of time, not angle.

• Radian is the SI unit of angle.