The type of spike used for fixing chairs of bull headed rails to wooden sleepers is A. Dog spike B. Rail screw C. Elastic spike D. Round spike

The correct answer is: A. Dog spike

A dog spike is a type of spike used for fixing chairs of bull headed rails to wooden sleepers. It is a long, thin spike with a blunt tip and a square head. The spike is driven into the sleeper through the chair, and the square head prevents the spike from rotating. Dog spikes are typically made of steel or iron, and they are coated with a rust-resistant material.

The other options are incorrect for the following reasons:

• A rail screw is a type of screw used for fastening rails to sleepers. It has a threaded shaft and a head that fits into a hole in the sleeper. Rail screws are typically made of steel, and they are coated with a rust-resistant material.
• An elastic spike is a type of spike that is used to fasten rails to sleepers in areas where there is a lot of vibration. It has a spring-loaded head that absorbs the vibration and prevents the rail from loosening. Elastic spikes are typically made of steel, and they are coated with a rust-resistant material.
• A round spike is a type of spike that is used for general carpentry work. It has a round head and a tapered shaft. Round spikes are typically made of steel, and they are not coated with a rust-resistant material.