Final answer:
The typical duration of a focus group is one to three hours.
Step-by-step explanation:
The typical duration of a focus group is usually one to three hours (C). This allows for enough time to gather sufficient data and insights from the participants without causing fatigue or loss of interest. The length of the focus group can vary depending on the complexity of the topic being discussed and the number of participants involved. However, it is important to keep the duration within a reasonable timeframe to ensure meaningful and productive discussions.