The molarity of a solution is defined as the number of moles of a solute dissolved in 1 litre of a solution. The given solute is NaCl and its molar mass is 58.44 ~ 58.5 g. Therefore, a 1M solution of NaCl will contain 58.5g of NaCl dissolved in 1 litre of solvent.

The molarity of the given NaCl solution is given by the formula

= = 0.1/0.5 = 0.2M or 0.2 mol L^-1.

The correct answer is (iii).