Which of the following weather conditions are conducive to in-flight icing?

In-flight icing occurs when supercooled water droplets come into contact with the aircraft surfaces and freeze, leading to ice accumulation which can impair the aircraft's performance. Among the options provided, the condition that is particularly conducive to in-flight icing is the presence of visible rain with temperatures below 0 degrees Celsius.

At temperatures below freezing, liquid water can still exist in a supercooled state. When rain falls in such conditions, it can be composed of these supercooled droplets. When these droplets hit the aircraft, they freeze instantly upon contact, creating ice. This is especially hazardous because it can accumulate on critical surfaces such as wings and tail, leading to increased weight and altered aerodynamics.

While visible rain at temperatures below 5 degrees Celsius or below 10 degrees Celsius may also contribute to icing potential, rain that is specifically observed at temperatures below 0 degrees Celsius is the ideal condition for in-flight icing. Higher temperatures, even if the rain is visible, are generally less likely to result in icing because the water is more likely to be in a non-supercooled state and will not freeze upon contact with the aircraft.

Thus, the correct response points to the specific conditions that favor in-flight icing, which is when visible rain occurs at temperatures