A redox (reduction-oxidation) reaction is a chemical reaction which involves loss or gain i.e transfer of electrons between two interacting systems.
The atom which loses electrons is said to have undergone oxidation and is termed as a reducing agent.
While the corresponding atom which gains electron undergoes reduction and is termed as an oxidising agent.
In this case we have:
2Na(s) + Cl2(g) → 2NaCl(s)
Here: The oxidation state of Na changes from 0 to +1
The oxidation state of Cl changes from 0 to -1
Thus, Na atoms loses electron and get oxidized
Cl atoms gain electron and get reduced.
The correct options are:
-Sodium atoms are oxidized
-Sodium transfers electrons to chlorine