Which element can be molded and hardened?

The element that can be molded and hardened is metal. Metals are known for their malleability and ductility, which allow them to be shaped into various forms when subjected to heat and pressure. Once shaped, metals can be cooled, which results in hardening and setting of the material into the desired form. This property is utilized extensively in various applications, from manufacturing tools to constructing buildings, where specific shapes and strengths are required.

In contrast, wood is a natural material that can be cut and shaped, but it does not undergo a hardening process in the same way metals do. Earth, in the form of clay or other materials, can be shaped and fired to harden, but it is not as versatile or common in everyday use as metal. Fire, while a crucial element for heating and transformation, does not possess physical form or the ability to be molded into shapes. Thus, metal stands out as the element that can effectively be molded and hardened, making it the correct choice.