E‌cell ‌=E‌cell ‌∘+0.06 (a) Cd(X) and Ni(Y)E‌cell ‌∘=+0.4−0.24;E‌cell ‌=0.22 (b) Cd(X) and Fe(Y)E‌cell ‌c=−0.04;E‌cell ‌=0.02 (c) Ni(X) and Pb (Y) E‌cell ‌∘=0.11;E‌cell ‌=0.17 (d) Ni(X) and Fe (Y) E‌cell ‌∘=−0.2;E‌cell ‌=−0.14 Since in (a) (b) (c), Ecell is positive, hence answer is (a) (b) (c).