While troubleshooting a circuit in an engine room central control console, a resistor is suspected of being faulty. Which of the following precautions must be observed if an analog or digital multimeter set up as an ohmmeter is to be used to check its value?

Correct Answer: Option A — Resistor's circuit must be de-energized and at least one end of the resistor isolated by disconnecting.

To accurately measure resistance, the ohmmeter must apply its own voltage. The circuit must be de-energized, and one end of the resistor isolated to prevent parallel paths from influencing the reading, a critical safety and accuracy precaution under 46 CFR Subchapter J.