In a solution with 0.1 M KCl and 0.1 M MgSO₄, how do these non-common ions affect the pH measurement?

• A. They have no effect on ionic strength or pH.
• B. They decrease ionic strength, leading to a higher pH.
• C. They increase ionic strength, affecting activity coefficients and altering pH.
• D. They increase ionic strength but do not affect pH.

Answer: (C)