Ordinary soft solder is primarily a mixture of which two metals?

Ordinary soft solder is primarily a mixture of lead and tin. This alloy is used in various applications, particularly in electronics and plumbing, due to its excellent properties, such as low melting point and good wetting characteristics.

Lead and tin, when combined, create a solder that melts at a relatively low temperature compared to many other metals, making it suitable for joining electronic components without damaging them. Additionally, the combination allows for good flow and adhesion to surfaces, which is critical for effective soldering.

The other choices represent different metal combinations that are not used for soft soldering. Copper and zinc form brass, which is used for different purposes, while nickel and silver may be used in specialized alloys for specific applications, not for ordinary soft soldering. Aluminum and iron do not form a solder material favored in any traditional soldering application, as their properties don't lend themselves well to effective joining like lead and tin do.