Which of the following is TRUE regarding the ignition of flammable gases?

Flammable gases can ignite when they come into contact with an appropriate ignition source, such as an open flame, spark, or hot surface. This is a fundamental principle of combustion; a mixture of fuel (in this case, the flammable gas) and an oxidizer (typically oxygen in the air) needs to reach a certain energy level provided by the ignition source to initiate burning.

It is also important to consider that although conditions such as pressure and temperature can influence the ignition process, they are not the sole requirements for ignition. The presence of an appropriate ignition source is the key factor that allows flammable gases to ignite. This means that under the right conditions, even low-pressure gases can ignite without needing high temperatures or pressures to do so.

Other options suggesting high pressures, high temperatures, or the absence of ignition sources do not accurately represent the requirements for the ignition of flammable gases.