The correct answer is: B. Rectangular
A rectangular footing is the most common type of footing used for two equal columns. It is simple to construct and can be easily adapted to different soil conditions. Rectangular footings are also relatively inexpensive to build.
A square footing is another option that can be used for two equal columns. However, square footings are not as efficient as rectangular footings in terms of load-bearing capacity. This is because square footings have a larger surface area than rectangular footings of the same width and length.
A trapezoidal footing is a less common type of footing that can be used for two equal columns. Trapezoidal footings are more efficient than square footings in terms of load-bearing capacity. However, they are also more difficult to construct and are more expensive to build.
A triangular footing is the least common type of footing that can be used for two equal columns. Triangular footings are the most efficient type of footing in terms of load-bearing capacity. However, they are also the most difficult to construct and are the most expensive to build.
In conclusion, the rectangular footing is the best option for two equal columns when the width of the foundation is restricted. It is simple to construct, can be easily adapted to different soil conditions, and is relatively inexpensive to build.