The correct answer is: A. wooden sleepers.
Dog spikes are used to fix rails to wooden sleepers. They are made of steel and have a pointed end that is driven into the sleeper. The other end of the spike has a head that is wider than the sleeper, which helps to keep the rail in place.
CST-9 sleepers are made of concrete and are not suitable for use with dog spikes. Steel trough sleepers are also made of concrete and are not suitable for use with dog spikes. Concrete sleepers are typically held in place with concrete dowels or bolts.
Here is a diagram of a dog spike:
The dog spike is driven into the sleeper with a hammer. The pointed end of the spike penetrates the wood, and the wider head of the spike prevents the rail from moving.
Dog spikes are an important part of railway infrastructure. They help to keep the rails in place and ensure that trains can travel safely and smoothly.