The density of water is 1g/cc, so if you do dimensional analysis, you can find that in 1 L of water, there is 55.56 mol.
Water density is: 1g/cc
1ml * 1g/ml = 1g of water in 1 ml.
Water molecular weight, about: 18g/mol
1g * 1mol/18g = 1/18 moles = about 0.0556 moles in 1ml (=1g) of water.
So, in 1 L, there will be 55.6 moles.
Therefore, in 2L of water there will be 2*55.6 moles
So, the correct answer is (b)