Amalgam, alloy of mercury and one or more other metals. Thus, option C is right ans.

Answer:
The metal that is always a constituent of an amalgam is Mercury.
Explanation:
Amalgam is a type of alloy that is formed by combining mercury with one or more other metals. It is commonly used in dentistry for dental fillings. Here is a detailed explanation:
- What is an amalgam?
- An amalgam is a mixture or alloy of mercury with another metal or metals.
- It is typically a solid material that has a silver-like appearance.
- Why is mercury always a constituent of an amalgam?
- Mercury plays a crucial role in the formation and properties of amalgams.
- It acts as a "binder" or "matrix" that holds the other metals together.
- Mercury has the ability to form a liquid phase, allowing it to mix and react with other metals.
- Other metals commonly used in amalgams:
- While mercury is always present in an amalgam, the other metal(s) can vary.
- Common metals used in dental amalgams include silver, tin, copper, and zinc.
- The specific combination of metals used in an amalgam depends on the desired properties and application.
- Properties and uses of amalgams:
- Amalgams are known for their strength, durability, and resistance to corrosion.
- They have been widely used in dentistry for dental fillings due to their ability to withstand the forces of chewing.
- Amalgams are also used in various other applications, such as electrical contacts and mirrors.
In conclusion, while mercury is always a constituent of an amalgam, the other metal(s) can vary depending on the desired properties and application.