Consider the reaction below.

2 upper I superscript minus (a q) plus upper C l subscript 2 (g) right arrow 2 upper C l minus (a q) plus upper I subscript 2 (a q).

Which half reaction correctly describes the reduction that is taking place?
Upper C l subscript 2 9 g) plus e superscript minus right arrow 2 upper C l superscript minu (a).
Upper C l subscript 2 (g) plus e superscript minus right arrow 2 upper C l superscript minus (a q).
2 upper I superscript minus (a q) right arrow upper I subscript 2 (a q) plus 2 e subscript minus.
2 upper I superscript minus (a q) right arrow upper I subscript 2 (a q) plus e superscript minus.