The aromatic oils of chaparral
a. promote wildfires
b. make many plants flavorful cooking herbs
c. shrubs eliminate their competitors
d. all of the above

D all of the above Chaparral shrubs tend to dominate in the lead up to a large cleansing fire. The oils promote wildfires, can be used for cooking and also are deadly to competitors. Thus before a large wildfire typically only certain chaparral shrubs dominate the landscape, and are often partially the cause and the vector of spread for the fire.