A fuse marked 250V, 650mA can be used in circuits with an "open fuse" supply voltage of:

The correct interpretation of a fuse marked with a voltage rating of 250V and a current rating of 650mA is that it is designed to operate safely in circuits with a maximum voltage of 250 volts. This means that the fuse will effectively protect the circuit from overcurrent conditions without risk of breakdown or failure due to voltage exceeding its rating.

In the context of the question, "open fuse" refers to the maximum voltage that can be applied across the fuse terminals when it is not conducting current (or has blown). When choosing an appropriate fuse for a circuit, the voltage rating is critical because using a fuse with a voltage rating lower than the circuit voltage could result in failure of the fuse to protect the circuit.

The other options presented, although potentially indicating lower voltages, do not align with the rated maximum voltage of the fuse. Specifically, using a fuse in circuits with a voltage higher than its rated 250 volts poses a safety risk, while choices like 12 volts or 125 volts do not make efficient use of the fuse's capabilities. Therefore, circuits with an open fuse supply voltage of up to but not exceeding 250 volts are suitable for the fuse in question, allowing it to function properly within its specifications.