Procedure 1: Apply the pH calculation formula The pH value of a solution is determined using the formula:\[\text{pH} = -\log[\text{H}^+]\]In this equation, \( [\text{H}^+] \) represents the molar concentration of hydrogen ions within the solution.Procedure 2: Input the provided concentration value Provided data:- \( [\text{H}^+] = 1 \times 10^{-3} \, \text{mol/L} \).Substitute this value into the formula:\[\text{pH} = -\log(1 \times 10^{-3}) = 3\]Conclusion: Consequently, the solution's pH is 3. This corresponds to option (1).