What unit measures the capacity of a conductor to resist electrical current?

The correct choice is the unit that measures the capacity of a conductor to resist electrical current. This is defined as resistance in an electrical circuit, and the unit of measure for resistance is the ohm. When a conductor has a higher resistance (measured in ohms), it impedes the flow of electrical current more significantly.

In the context of electronics, resistance is a fundamental property that determines how much current will flow through a conductor when a specific voltage is applied. The relationship among voltage, current, and resistance is expressed in Ohm's Law, which states that voltage equals current times resistance (V = IR).

The other units listed serve different purposes: volts measure electric potential, amperes measure the flow of electric current, and watts measure electrical power (the rate at which electrical energy is consumed or produced). Therefore, ohm is clearly the correct answer as it is specifically designed to quantify resistance in electrical conductors.