What is the area of a square with a side length of 4?

To find the area of a square, you use the formula:

[ \text{Area} = \text{side length} \times \text{side length} ]

In this case, the side length of the square is 4. Therefore, you calculate the area as follows:

[ \text{Area} = 4 \times 4 = 16 ]

This calculation shows that the area of the square is 16 square units. Since the area of a square increases with the square of its side length, it is essential to perform the multiplication correctly to arrive at the right answer. Given that 16 is the product of 4 multiplied by itself, it confirms that option C is the correct choice. The other numbers do not accurately reflect the relationship between the side length and its area according to the geometric principles governing squares.