Alloys are a mixture of two or more metals, or a metal and a non-metal, that are combined to obtain specific desired properties. The best method for preparing alloys is by cooling a molten mixture of the metals.
In this method, the metals are heated to their melting points, and then mixed thoroughly while in the molten state. The mixture is then allowed to cool, and the metals solidify to form an alloy. This process is called casting.
The advantage of this method is that the metals mix together uniformly in the molten state, which leads to a homogeneous distribution of the constituent elements in the alloy. This ensures that the desired properties of the alloy, such as strength, durability, and resistance to corrosion, are consistent throughout the material.
Other methods like reducing a mixture of their metallic oxide, electroplating, and arc-welding may be used to prepare alloys, but they are not as effective as cooling a molten mixture of the metals.
Therefore, the correct answer is cooling a molten mixture of the metals.