If the burning of wood for fuel is harming our nation, then, according to the specificity rule, the best policy to use to mitigate this harm (out of the four listed here) is.

a. subsidize research and development on alternate fuel sources.
b. levy taxes on cutting down trees whose wood can be used as fuel.
c. impose tariffs on the importation wood that can be used as fuel.
d. tax the consumption of wood used as fuel .