Which of the following is true regarding carbon content in steel?

In the context of steel, increased carbon content plays a significant role in determining its mechanical properties. When the carbon content in steel is elevated, it enhances certain attributes like hardness and tensile strength, but it also introduces a tendency towards brittleness. This brittleness arises because higher carbon levels can disrupt the ductile microstructure of steel, making it less able to deform under stress without breaking.

Brittleness means that while the steel may be strong and hard, it is more likely to fracture under impact or loading conditions, as it cannot absorb energy effectively without failing. The balance between strength and ductility is crucial in applications like auto body repair, where materials need to withstand impact while maintaining some degree of flexibility to prevent catastrophic failure.

In contrast, lower carbon content generally leads to a more ductile and tough steel, which is often preferred in applications where resilience is necessary. This explains why increased carbon content leads to brittleness, distinguishing it from the other options that do not accurately represent the relationship between carbon content and steel properties.