Question

Which expression correctly represents a balanced reduction half-reaction?

Answer 1

for answering for the question, there exists four choices:
1) Na+ + e- -------------- Na
2) Na --------Na+ + e-
3) Cl2 + 2e- ------------ Cl-
4) 2Cl- ---------Cl2 + 2e-

reduction half-reaction general formula is
oxidant + e - or + -------- Product

so in our case the answer is
1) Na+ + e- -------------- Na (exactly balanced)