Which one of the following changes will cause a DECREASE in the cell voltage

For the galvanic cell

Ni (s) | Ni2+ (1 M) || H+ (1 M) | H2 (1 atm) | Pt (s),

which one of the following changes will cause a DECREASE in the cell voltage?

a) Increasing the pressure of H2 to 2.0 atm
b) Decreasing the mass of the nickel electrode
c) Lowering the pH of the cell electrolyte
d) Decreasing the concentration of Ni2+ ion
e) Decreasing the mass of the platinum electrode

Also, can you tell me what effect the other four options will have on the voltage of the cell?

E0(Ni/Ni+2) = +0.25Volt
Ni -----------------> Ni+2 + 2e
2H+ + 2e-------> H2
=====================
Ni + 2H+ ---------> Ni+2 + H2
=====================
Ecell = E0Cell -0.0591/2 log[Ni+2]* pH2/[H+]2
Ecell = E0Cell + 0.0591/2 log[H+]2/[Ni+2]*pH2
Decrease in cell voltage will be caused by increasing the pressure of H2 to 2 atm ie choice (a) as pH2 comes in the denominator in the 2nd equation.
Increasing or decreasing the mass of the nickel or platinum electrode will have no effect on EMF as solids have an active mass of 1 as per IUPAC
Lowering the pH of the cell electrolyte means raising the H+ ion concentration, now as H+ lies in the numerator it will cause the cell voltage to increase.
On the other hand decreasing Ni+2 conc will also cause the cell voltage to increase as Ni+2 again lies in the denominator.