What action must be taken regarding engine inlets before flight in icing conditions?

In icing conditions, it's essential to ensure that the engine inlets are free of any frozen contaminants before flight to maintain engine performance and safety. Ice or snow accumulation in the engine inlets can disrupt the airflow into the engines, potentially leading to reduced engine efficiency or even engine failure. Therefore, before departing, the inlets should be de-iced to remove any ice or snow and then checked to confirm that there are no remaining frozen contaminants. This action is crucial to ensure that the engines receive the necessary airflow and operate correctly during the flight.

The other options lack the necessary emphasis on the importance of preparing engine inlets for safe operation in icing conditions, making them less suitable for maintaining safety and performance in such environments.