How is the voltmeter connected across the points between which the potential difference is to be measured?

In parallel

The correct answer is option 2. In parallel.

When measuring the potential difference (voltage) between two points in a circuit using a voltmeter, the voltmeter is connected in parallel across those points.

In electrical terms, connecting devices in parallel means that each device is connected across the same two points in a circuit, forming branches that share the same voltage. This ensures that the voltmeter measures the potential difference accurately without affecting the circuit's operation.

In practical terms, connecting the voltmeter in parallel involves connecting the positive terminal of the voltmeter to the point at higher potential (usually labeled as positive) and the negative terminal to the point at lower potential (usually labeled as negative). This setup allows the voltmeter to measure the voltage difference directly across the two points without altering the current flow in the circuit.