Answer:
The correct answer is C. Frequency.
Explanation:
In statistics, frequency is called the period of time that elapses between a certain event developing and repeating itself again. That is, the frequency measures the duration of the process of repetition of a certain event.
Thus, for example, if an earthquake occurs exactly every 4 months in a certain place, this natural catastrophe occurs with a frequency of 4 months.
Therefore, if the limits of a certain type of aquafarming pest during the farming of catfish might not to recur more than once every 6 months, this expression refers to the frequency with which said event must (or in this case, not must) happen.