Why does the matchstick start burning on rubbing it on the side of the matchbox?

Ignition temperature is reached

The correct answer is option 1. Ignition temperature is reached.

The lowest temperature at which a substance catches fire is called its ignition temperature.

A matchstick does not catch fire on its own at room temperature.

Matchstick start burning on rubbing it on the side of the matchbox as the matchstick head produce enough heat (Ignition temperature reached) to ignite antimony trisulphide and start the combustion.