Metals are known for many particular properties, and one of these properties is conductivity, which is the ability to conduct electricity for a given element, and most of the metals, due to its low electronegativity, can conduct electricity, and in our question, we have 3 types of metals, Iron, Copper and Gold, all 3 are great electrical conductors, we are left with wood, which is a common insulator, due to air pockets within its cellular structure, therefore letter C