Think about the article. What caused Joseph Montgolfier to get the idea to make a hot air balloon?

He heard that the townspeople in Annonay needed a safe way to travel to Paris.
He witnessed a giant bag surge into the air and crash down in a field.
He was told that the king of France demanded to see a machine capable of flight.
He noticed a shirt billowing upward while it was drying over a fire.

He noticed a shirt billowing upward while it was drying over a fire.