Select the option in which the words share the same relationship as that shared by the given pair of words.
Length : Metre

Given: Length : Metre

Logic: The meter is the unit to measure length.

Let's check the options:

First option: Mass : Gram; The gram is the unit to measure mass.

Second option: Second : Time; The second is the unit to measure time, but the order of words is not the same.

Third option: Gravity : Force; Force is not a unit to measure gravity.

Fourth option: Kelvin : Temperature; The kelvin is the unit to measure temperature, but the order of words is not the same.

So, the correct answer is (a).