Final answer:
Case hardening of low carbon steel creates a high carbon outer surface for increased hardness while maintaining a soft, ductile low carbon inner core, denoted by option E.
Step-by-step explanation:
Case hardening of low carbon steel is a process used to increase the hardness of the outer surface while maintaining a soft, ductile inner core. This is achieved by increasing the carbon content at the surface of the steel, through techniques such as carburizing, where carbon is diffused into the outer layers of the steel. High carbon steel, which contains up to about 1.5% of carbon, is known for its hardness, but it is also more brittle than steel with less carbon content. On the other hand, mild steel contains up to about 0.25% carbon and is stronger and harder than pure iron but still less hard than high carbon steel. Therefore, the correct answer to the question is E, which states that case hardening produces a low carbon inner core and high carbon outer surface.