Answer: Option A
Explanation: 2 Na + Cl2---> 2NaCl
Here Oxidation no of Na is zero while in NaCl is +1. That means oxidation state of Na increased from 0 to +1 hence oxidation
While Cl2 has zero in molecular form and -1 in NaCl hence Reduction (Oxidation no decreased from zero to -1)
Halogens(cl) always shows -1 oxidation state and IA group elements(Na)shows +1 oxidation state