The circuit diagram containing a cell, a key, a resistor of `2 Omega` in series with a combination of two resistors (`4Omega` each) in parallel and a voltmeter across the parallel combination is shown below
The resistance of parallel combination of two resistors (`4Omega` each) is `2Omega`.
The same current passes through the `2Omega` resistor and `2Omega` (equivalent of two parallel resistor of `4Omega`). So, voltage drop by them will be same, hence the voltage V is same across `2Omega` resistor and the parallel combination of two resistors, cell of `4Omega`.