The correct option is C 4 units
A square has four equal sides and four equal angles. Hence, a square is a regular quadrilateral.
Here, its given that the area of the square is 16 sq units.
Now, area of a square = side × side =16 sq units
⇒ Side2 = 16 sq units
⇒ Side = 4 units.
Therefore, length of the side of the square is 4 units.