Which are the materials generally employed as solder in soldering operation in electronics?

The correct answer is B) Lead and tin.

Explanation:

1. B) Lead and tin: Traditionally, and still commonly, solder used in electronics is an alloy of lead and tin. A typical composition is 60% tin and 40% lead (or 63% tin and 37% lead for eutectic solder). This alloy has a low melting point, good electrical conductivity, and excellent wetting properties, making it ideal for joining electronic components. While lead-free solders are now prevalent due to environmental concerns, lead-tin was the standard for a very long time and is still "generally employed" in many contexts.
2. A) Iron and tin: Iron has a very high melting point (1538 °C) and is not suitable for solder, which requires a low melting point (typically below 300 °C).
3. C) Aluminium and lead: Aluminium is generally difficult to solder due due to the rapid formation of a tenacious oxide layer. It is not a common component in electronic solders.
4. D) Aluminium and iron: Both aluminium and iron have high melting points and are not suitable as solder materials for electronics.