Solder used for joining metal surfaces should have a __________.

Correct Answer: Option A — melting point lower than that of the metals being joined

Soldering is defined by the use of a filler metal with a melting point below 840°F (450°C) and below that of the base metals being joined. This allows the joint to be formed through capillary action without melting or structurally altering the parent metal of the components.