Whatever cycle you are driving on, you must not drive unless you have had at least 24 consecutive off-duty hours at some point in the preceding...?

Answer: C — 14 days

In this question, the key is to recognize the word "consecutive." This means that the off-duty hours must be uninterrupted and consistent. Option A is incorrect because it is only a weekly cycle and does not guarantee 24 consecutive off-duty hours. Option B has a longer time frame of 10 days but again, it does not ensure that the 24-hour requirement is met consecutively. Option D is even longer at 21 days and does not meet the requirement. Therefore, option C is the most accurate option as it ensures that the 24 consecutive off-duty hours are met within a 14-day cycle.