The correct answer is C. Carbon and manganese.
Carbon is the main alloying element in steel, and it is responsible for the strength and hardness of the material. Manganese is also an important alloying element, and it helps to improve the toughness and wear resistance of steel.
Silicon is not an important constituent in the composition of steel used for rail. It is a relatively weak element, and it can make the steel more brittle. Phosphorous is also not an important constituent in the composition of steel used for rail. It is a non-metallic element that can cause embrittlement in steel. Sulphur is also not an important constituent in the composition of steel used for rail. It is a non-metallic element that can cause hot shortness in steel.
Here are some additional details about the importance of carbon and manganese in steel:
- Carbon is the main alloying element in steel, and it is responsible for the strength and hardness of the material. The amount of carbon in steel is typically between 0.02% and 2.11%. The higher the carbon content, the stronger and harder the steel will be. However, too much carbon can make the steel brittle.
- Manganese is also an important alloying element, and it helps to improve the toughness and wear resistance of steel. The amount of manganese in steel is typically between 0.5% and 1.5%. Manganese also helps to prevent the formation of cracks in steel.
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