Final answer:
Rick Brown's actions and the weather conditions were the cause of the fire.
Step-by-step explanation:
The cause of the fire was both Rick Brown's actions and the weather conditions. While Brown's actions of dragging a piece of steel behind a vehicle and sending sparks into the brush may have started the fire it was the weather conditions that caused the fire to spread. The severity of a forest fire is influenced by the availability of plant life to burn and the dryness of the fuel. Therefore both factors contributed to the cause and spread of the fire.