The correct answer is A) less brittle. When metal is tempered, it undergoes a heat treatment process that increases its toughness and ductility, making it less brittle. The tempering process involves heating the metal to a specific temperature, holding it at that temperature for a certain duration, and then cooling it. This process relieves internal stresses, increases the metal's ability to withstand impact and deformation, and improves its overall mechanical properties. The other options are incorrect because tempering does not make the metal more brittle (B), less tough (C), or harder (D). In fact, the tempering process is specifically designed to enhance the metal's toughness and ductility, which are the opposite of being more brittle or less tough.