The correct answer is: A. One cantilever.
A T-shaped retaining wall is a type of retaining wall that is shaped like the letter “T”. It consists of a vertical stem and a horizontal slab that extends from the stem. The slab is cantilevered, meaning that it projects beyond the support of the stem. This type of wall is often used to retain soil or other materials that are prone to erosion.
The other options are incorrect because they do not accurately describe the structure of a T-shaped retaining wall. Option B states that a T-shaped retaining wall consists of two cantilevers. However, a T-shaped retaining wall only has one cantilever, which is the horizontal slab that extends from the stem. Option C states that a T-shaped retaining wall consists of three cantilevers. This is also incorrect, as a T-shaped retaining wall only has one cantilever. Option D states that a T-shaped retaining wall consists of four cantilevers. This is the most incorrect option, as a T-shaped retaining wall only has one cantilever.