prep162

162. 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, thev 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

这里在从句和主句之间加了一个doing作状语，不会引起修饰歧义吗？不知道是修饰前面的从句还是后面的主句。

当然从逻辑句意上来说，这里是上半层的意思。

是不是通过这道题能推断出这样的表达不算歧义的？

最头痛歧义的判断了，算与不算好像都是ets说了算：（