1. Key idea about an ideal voltmeter

   An ideal voltmeter has infinite resistance, so no current flows through it.

   Therefore, the branch containing the voltmeter is effectively an open circuit.

2. Consequence for the given circuit

   Since no current can pass through the voltmeter branch, the two terminals across which the voltmeter is connected must be checked for potential difference.

   In the shown arrangement, because the voltmeter branch is open, there is no current through the relevant part of the circuit that could produce a voltage drop between those two points.

   Hence, the two points connected to the voltmeter are at the same potential.

3. Voltmeter reading

   The reading of the voltmeter is therefore $V = 0\ \text{V}$

4. Option check

   • A: $3\,\text{V}$ — incorrect
   • B: $10\,\text{V}$ — incorrect
   • C: $5\,\text{V}$ — incorrect
   • D: $0\,\text{V}$ — correct

5. Final answer

   $\boxed{0\ \text{V}}$

So the correct option is D.