The relevant range is that range of activity where:

A) management may not find it important to concern itself.
B) management does not expect the firm to operate.
C) fixed costs remain unchanged.
D) the expected costs exceed the benefits from the activity.

The relevant range is the range of activity where fixed costs remain unchanged. Therefore, option C is the correct answer. Option A and B are incorrect because management always concerns itself with the relevant range and expects the firm to operate within it. Option D is also incorrect because if the expected costs exceed the benefits from the activities, management would not continue with those activities and would look for more profitable options within the relevant range.