Solder is an alloy made of:

A blend of metals, consisting of two or more, is referred to as an alloy. The end result is a product with strong strength, good mechanical qualities, and good chemical properties. By first heating the two metals, solder is used to connect them.

Soldering is a kind of process where different varieties of metals are joined together by melting solder (an alloy) at high temperatures.
Solder is generally used to make strong permanent bonds say for example, joining copper wire in the electrical boards, etc.
There are three types of soldering that are generally used-
Firstly, soft soldering which is used at a temperature between ${90}^{\circ }C$ to ${450}^{\circ }C$. In this method the temperature used is too low, so it thermally stresses the components. But the joints formed are not too strong. Hence this method is not used for heavy load bearing systems and also not used in high temperatures as the solder melts and loses its strength.

Second, temperatures higher than 450°C are utilised for hard soldering. The major bonding metals used in this procedure are silver and brass. Here, a blowtorch is typically utilised to achieve such a high temperature.
Thirdly, another technique that is employed in the same temperature range as above is brazing. Unlike the other two techniques, the metal utilised here has a very high melting point. Here, a solid and enduring link is created.
Metals typically used to make solder are tin, lead, and other eutectic metals.

In this procedure, hot iron heated to a temperature of at least 600 °F is used to melt the metals, after which the mixture is further cooled and a strong bond is created.

Hence, the correct option is (A).