Concept:The pH of a solution gives the concentration of hydrogen ions. For a strong dibasic acid like sulphuric acid, the acid concentration is half of the hydrogen ion concentration.Explanation:Given that the pH of the H2SO4 solution is 4.The hydrogen ion concentration is calculated from the pH as:[H+]=10−pH=10−4MSulphuric acid dissociates completely in water as:H2SO4→2H++SO42−Thus, one mole of H2SO4 produces two moles of H+ ions.If the molarity of the acid is M, then:[H+]=2MSubstituting the known value of [H+]:2M=10−4Solving for M:M=210−4=5×10−5MThis value matches the one given in the options.Answer:The molarity of the H2SO4 solution is 5×10−5M, which corresponds to option C.