c) Is conducted below the recrystallisation temperature
Explanation:
In cold working the metal goes through a process of plastic deformation that is conducted below its recrystallization point (which its usually at room temperature), this in order to change permanently the makeup of its crystals. The temperature at which the process happens is low enough so that atoms cannot rearrange themselves.
The resulting metal is more resistant to deformation, and has an increased hardness and tensile strength.
