Which tool is primarily used to measure electrical current in a circuit?

The correct choice is the multimeter, which is a versatile instrument capable of measuring multiple electrical values, including voltage, current, and resistance. When set to the appropriate function, a multimeter can effectively measure electrical current in a circuit, which is typically expressed in amperes. This adaptability makes it a valuable tool for troubleshooting and electrical work, allowing technicians to interpret various electrical parameters without the need for multiple specialized devices. Although other tools can measure current, like an ammeter (which is a type of multimeter), the general utility and functionality of a multimeter make it the most commonly used instrument for this purpose.