What should be avoided during the application of deicing fluid to prevent forcing ice into control areas?

The correct answer emphasizes the importance of avoiding the direct application of deicing fluid at flight controls, as this could lead to ice being forced into those control areas. When deicing fluid is applied directly onto flight controls, especially under high pressure, it can inadvertently create a situation where ice or contaminants are pushed into the mechanisms that govern those controls. This could cause malfunction or reduced effectiveness of the flight control systems, posing a risk during flight operations.

In contrast, while high-pressure spraying and using diluted mixtures carry their own risks, the primary concern highlighted in the question is the potential for compromising the integrity of the flight control systems by forcing unwanted substances into them. Thus, maintaining a careful approach when applying deicing fluid is crucial to ensure both safety and operational effectiveness. Not spraying at all would not address the need to remove ice, whereas managing the technique of application is key to an effective deicing process.