The paradox we are trying to explain is that rain means less fires, but the fires that do happen when it is rainy tend to be more damaging.
I don't see how B is relevant to this. This sets up a new distinction between where fires are more or less common, but does nothing about what we care about- when brush fires happen.
C gives us a reason that rainy fires are more damaging. Since rain promotes vegetation, more rain means more fuel for the fires. So, the fires after it rains will tend to be bigger and more damaging than those during a drought, when there is comparatively little vegetation.