Passage: In the small town of Oakey Oaks, Chicken Little rings the school bell and warns everyone to run for their lives. This sends the whole town into a frenzy. Eventually, the Head of the Fire Department calms down enough to ask him what is happening. Chicken Little says that a piece of the sky shaped like a stop sign had fallen on his head, but he is unable to find the piece. His father, Buck Cluck, assumes that this "piece of sky" and was just an acorn that had fallen from the tree, making Chicken Little the laughingstock of the town.

Question: What is the primary way of alerting people of danger in Oakey Oaks
school bell