The correct answer is: A. Raft foundation
A raft foundation is a continuous concrete slab that supports a number of columns or walls. It is used to transmit heavy loads through steel columns to the underlying soil. Raft foundations are often used in areas with poor soil conditions, as they provide a more uniform distribution of load than other types of foundations.
A grillage foundation is a grid of steel beams or concrete slabs that is used to support a number of columns or walls. It is similar to a raft foundation, but it is more flexible and can be used in areas with a wider range of soil conditions.
A well foundation is a deep, cylindrical concrete foundation that is used to support a single column or wall. It is used in areas with poor soil conditions, as it provides a more stable foundation than other types of foundations.
An isolated footing is a small, rectangular concrete foundation that is used to support a single column or wall. It is used in areas with good soil conditions, as it is a relatively simple and inexpensive type of foundation.
In summary, a raft foundation is the best type of footing to use to transmit heavy loads through steel columns. It is a continuous concrete slab that supports a number of columns or walls, and it is used to transmit heavy loads to the underlying soil.