Which of These Is Not a Method Used by Utilities

Which of these is not a method used by utilities to reduce sulfur dioxide emissions?

A) Burning low-sulfur coal.
B) Crushing and washing coal to remove sulfur.
C) Burning coal at high temperatures to break down the sulfur.
D) Employing flue gas scrubbers in smoke stacks which traps sulfur dioxide.
E) All of these are current methods utilities are using to lower SO₂ emissions.