21. Which Beaufort force indicates a wind speed of 65 knots?

Beaufort force 12 is the correct answer because it corresponds to wind speeds of 64 knots or greater, encompassing a 65-knot wind. The Beaufort scale is a standardized system ranging from 0 to 12, with force 12 representing hurricane-force winds. Values outside this range, such as 6.5 or 15, are not part of the standard scale, and lower forces represent significantly lower wind speeds.