Which of the following solution is more concentrated
 

Given data: It is given to identify that which of the following solution is more concentrated.

0.3% H₃PO₄ means 0.3 gm H₃PO₄ is present in 100 gm of solution.
0.3M H₃PO₄ means 0.3*98gm H₃PO₄ is present in 1 l of solution.
0.3m H₃PO₄ means 0.3*98gm H₃PO₄ is present in 1kg of solvent
0.3N H₃PO₄means 0.1M, which means 0.1*98gm H₃PO₄ is present in 1l of solution
by comparing all four options, we get 0.3*98gm  H₃PO₄ in 1l solution is more concentrated.

Hence option(B) 0.3M H₃PO₄ is correct.