The Minnesota Department of Natural Resources has introduced regulations that require the use of approved firewood in state parks, state forests and wildlife management areas. There is specific approved firewood for each area which can't be used in other protected areas. What is the most likely reason for these restrictions? A) To clear excess wood from trees that have fallen or been removed in the parks. B) To avoid the introduction or spread of insects or disease that damage native trees. C) To generate revenue for the department by restricting the sale of firewood by outside vendors. D) To eliminate the use of highly flammable firewood that might lead to uncontrolled forest fires.