Which half-reaction correctly represents reduction? OA) Ca2+ - Ca + 2e-

OB) Ca2+ + 2e-

Ca

O C)2 F- + 2e- - F2

OD) 2F- - F2 + 2e-

B. Ca2+   +  2e- >   Ca

Explanation:

Reduction involves the gaining of electrons as well as a decrease in the oxidation state of the atom or ion.

In this case; Ca2+ gains two electrons and the oxidation state is reduced from +2 to  0.

Ca2+   +  2e- >   Ca