To answer this question, we first want to think about the function of each pump! Ions are pumped across the membrane in specific channels that only allow the passage of the ion they are designed for (i.e. K+ channels pump K+ across the membrane and Na+ channels pump Na+ across the membrane).
For options A and B, we might need a little more information about which channel they are referring to, but in general, if they are referring to their specific channels, those would both be correct (they move their respective ion across the membrane) and would not be a difference between the channels in this respect.
When we look at option C, we're seeing that it refers to pH. pH is completely dependent on H+ levels. H+ levels is typically described in molarity, which is dependent on volume. If you take 2 H+ ions and put them in 1L of water, our H+ concentration would be 2 M. If you take 2 H+ ions and put them in 2 L of water, our H+ concentration would be 1 M. As you can see, the concentration of H+ ions, and therefore pH, would be affected by a change in water concentration. Therefore, the water movement that accompanies ion movement could affect pH.
When we look at option D, we see that it discusses a change in voltage. Voltage is driven by the balance of positive to negative ions on either side of the membrane. As these membrane channels are driven by ion movement across the membrane (the movement of positive charge as both Na+ and K+ ions are positively charged), this will change the balance of positive and negative charges across the membrane. Therefore, the movement of ions through these changes can cause a voltage change. However, it is the ions themselves that change the charge and not the water accompanying the ions. The water would only serve to dilute the charge.
