Although ice particles in the upper atmosphere benefit Earth in that they reflect and absorb solar radiation, acting as a global thermostat and thus keeping Earth from either burning up or freezing over, they also
accelerate the destruction of the ozone layer by reacting with chlorofluorocarbons (CFC’s).

(A) acting as a global thermostat and thus keeping Earth from either burning up or freezing over, they also
accelerate
(B) acting as a global thermostat and thus keeping Earth either from burning up or freezing over, while also
accelerating
(C) act as a global thermostat and thus keep Earth from either burning up or freezing over, while also
accelerating
(D) they act as a global thermostat that thus keeps Earth either from burning up or freezing over, even
though it also accelerates
(E) they act as a global thermostat to thus keep Earth from either burning up or freezing over, but they also accelerate