The correct answer is: A. Less than 0.25
Mild steel is a type of steel that has a low carbon content. The carbon content of mild steel is typically less than 0.25%. This means that mild steel is relatively soft and ductile, and it is easy to work with. Mild steel is often used in construction and manufacturing, as it is a strong and versatile material.
Option B is incorrect because the carbon content of mild steel is typically less than 0.25%. Option C is incorrect because the carbon content of mild steel is typically less than 0.7%. Option D is incorrect because the carbon content of mild steel is typically less than 1.5%.