Which of the following is an example of spontaneous combustion?

Burning of phosphorus at room temperature.

The correct answer is option 2. Burning of phosphorus at room temperature.

Gas burns rapidly and produces heat and light. Such combustion is known as rapid combustion.

Substances like phosphorus which burn in air at room temperature. This type of combustion in which a material suddenly bursts into flames, without the application of any apparent cause is called spontaneous combustion.

When a cracker is ignited, a sudden reaction takes place with the evolution of heat, light and sound. A large amount of gas formed in the reaction is liberated. Such a reaction is called explosion.