An "exothermic" connection is made by ...

The correct answer refers to an "exothermic" connection, which is made using a chemical process. This method typically involves a reaction that generates heat to fuse materials together. In an exothermic connection, a chemical mixture is ignited, leading to a reaction that produces molten metal, which then creates a strong bond between the conductive components—commonly used in lightning protection systems for reliable electrical connections.

Other options, while applicable in different contexts, do not describe the exothermic process. For instance, welding with electricity generally refers to a process that uses electric current to heat and melt metals together, rather than relying on a chemical reaction. A mechanical crimp involves physically compressing two conductors together, which does not involve heat generation through a chemical process. Using high-temperature solder involves melting a filler metal to create a joint, which also does not fulfill the criteria of an exothermic connection, as it relies on heat application rather than a chemical reaction to initiate bonding.