Solder is a metallic alloy used to join two metal surfaces. Which option describes solder?

• A. A natural fibre.
• B. A type of plastic.
• C. Metallic alloy of tin and lead that is used to join two metal surfaces.
• D. An alloy of copper and zinc.

Answer: (C)

Solder is a filler metal chosen to join metal parts by melting, flowing into the gap between surfaces, and then solidifying to form a bond. It’s typically a tin-based alloy, often with lead, which gives it a low melting point so it can melt without warping the pieces being joined. This makes it ideal for creating a strong, conductive joint between metal surfaces.

So, describing solder as a metallic alloy of tin and lead used to join two metal surfaces exactly captures its composition and purpose. The other options aren’t correct because natural fibre and plastic are non-metal materials, and brass is a copper-zinc alloy that isn’t used as a low-m melting filler metal for joining surfaces.