The correct option is D 50 M
Molarity =No. of molesVolume of solution
Let, volume of the solution be 1 litre
Given, density of D2O is 1 g mL−1
So, 1 litre of solution contains 1000 g solution.
∴
No. of moles=Total massMolar mass=100020=50 mol
Molarity=50 mol1 litre=50 M