Answer: It loses electrons to another element.
Explanation:- Oxidation is the process in which an element loses electrons and there is an increase in the oxidation state. On losing electrons it combines with a electronegative element such as oxygen, sulphur or nitrogen etc.

Reduction is the process in which an element gains electrons and there is a decrease in the oxidation state.

Answer:
[NaCl[ = 0.535M
Explanation:
We determine the moles of solute:
125 g . 1 mol/ 58.45 g = 2.14 moles
Molarity (mol/L) → 2.14 mol / 4L → 0.535M
Molarity is a sort of concentration that indicates the moles of solute in 1L of solution