Which of the following defines a competent ignition source?

A competent ignition source is defined as one that raises the fuel to its ignition temperature, thus allowing combustion to occur. This means that the source must provide sufficient energy in the form of heat to elevate the temperature of the fuel to the point where the fuel can vaporize and ignite.

When evaluating other options, a source of cold air does not provide heat and cannot initiate ignition. Similarly, a source that weakens the fuel does not inherently contribute to ignition but may instead affect the combustion process negatively. A source that does not produce heat also cannot serve as an ignition source since it fails to provide the necessary thermal energy to reach the ignition temperature of any fuel. Hence, the correct option highlights the essential characteristic of an ignition source capable of triggering combustion by supplying the requisite heat energy.