What is the formula for calculating the area of a rectangle?

The formula for calculating the area of a rectangle is determined by multiplying its length by its width. This is because the area represents the total space enclosed within the rectangle, and by multiplying these two dimensions, you obtain the number of square units that fit within that shape.

In the case of the correct choice, the multiplication directly reflects how many units of space are covered when these two sides are considered together. The rectangle's area is fundamentally based on its two defining dimensions, which are length and width.

Thinking about the other options: the first choice indicates addition, which does not accurately reflect how area is calculated. The second option involves height instead of the width, which might apply in other contexts, such as calculating the volume of a three-dimensional object but not area. Similarly, the fourth option also substitutes height instead of length, which is again not applicable to the two-dimensional calculation of area for a rectangle.