What should be avoided during extended flight in icing conditions?

During extended flight in icing conditions, deploying flaps and slats should be avoided because these components are designed to enhance lift and control at lower speeds and higher angles of attack. However, in icing conditions, the performance characteristics of the aircraft can be significantly altered due to ice accumulation on the wings and control surfaces. This buildup can lead to a decrease in lift effectiveness and an increased risk of stall, especially when flaps and slats are deployed.

In icing conditions, maintaining optimal performance and control of the aircraft is critical, and deploying flaps and slats may compromise safety. The other options, while potentially less than ideal under specific circumstances, do not carry the same immediate risks associated with increasing the chances of a stall or losing control in icy conditions. Therefore, avoiding the deployment of flaps and slats is a prudent measure to ensure safety during flights in such challenging environments.