Select the option that best completes the analogy: Ampere : Current :: Ohm : ?

The relation is unit : the quantity that unit measures. The ampere measures current, and the ohm measures resistance. Every distractor is a genuine electrical quantity with a unit of its own — voltage is measured in volts, power in watts and charge in coulombs — so each is tempting until the unit named in the question is matched to the one quantity it actually belongs to.