A detention time of 5 hours is within the usual 2-4 hour range.

• A. Yes
• B. No
• C. Depends on plant size
• D. Depends on flow condition

Answer: (B)

Detention time is the period water spends in a unit or basin, and there’s a typical guideline range used for design and operation. If the usual range is 2–4 hours, a value of five hours goes beyond that upper limit. So it isn’t inside the normal range. While actual detention time can vary with plant size or operating conditions, the question asks about the usual range, and five hours exceeds it.