The correct answer is D. 2 V.
When cells are connected in parallel, the voltage remains the same, but the current increases. This is because each cell is providing the same amount of voltage, but the current is split between the cells. So, if you have five 2 V cells connected in parallel, the output voltage will be 2 V, but the current will be five times the current of a single cell.
Option A is incorrect because the output voltage cannot be less than the voltage of any of the cells. Option B is incorrect because the output voltage cannot be a fraction of the voltage of any of the cells. Option C is incorrect because the output voltage cannot be greater than the voltage of any of the cells.