ANS:C - wood

An orthotropic material is indeed a special type of anisotropic material with unique mechanical properties along three mutually perpendicular directions. Each direction may have different mechanical properties such as stiffness, strength, and thermal expansion coefficients. An example of an orthotropic material is wood. Wood exhibits different mechanical properties along its longitudinal (grain direction), radial (perpendicular to the grain), and tangential (along the growth rings) directions. For instance, wood is typically stiffer and stronger along the grain compared to perpendicular to the grain. While materials like stainless steel, cast iron, and teflon may exhibit certain degrees of anisotropy due to factors like grain structure or processing conditions, they are not typically considered orthotropic materials because their mechanical properties do not vary independently along three mutually perpendicular directions in a predictable manner like wood.