On dissolving 1 mole of each of the following acids in 1 litre water, the acid which does not give a solution of strength 1N is -

Only if the acids have a basicity value or n factor equal to 1 can 1 mole of acid be dissolved in 1 liter of water yield a 1N solution. In other words, assuming the acid is monobasic, 1mole will provide 1 liter of 1N solution.
HCl, HClO₄, and HNO₃ are all monobasic (n factor=1), where as phosphoric acid, or H₃PO₄, has a basicity value of 3 and is tribasic in nature.

 Hence the answer is (D)Phosphoric acid.