The groups of hardwoods that are suitable for railway sleepers in Nigeria is?

Out of the given options, the group of hardwoods that are suitable for railway sleepers in Nigeria are mahogany, obeche, and iroko. Mahogany is a strong and durable hardwood with a natural resistance to decay, making it a popular choice for construction and outdoor use. Obeche, on the other hand, is a lightweight hardwood that is easy to work with and has good strength properties. Iroko is a dense and tough hardwood that is highly resistant to decay and insect attack, making it an excellent choice for outdoor applications. Railway sleepers need to be strong, durable, and able to withstand the heavy loads of trains passing over them, as well as the outdoor environment, which can be harsh in Nigeria. Mahogany, obeche, and iroko all have properties that make them suitable for railway sleepers, which is why they are commonly used for this purpose.