What does "NSC" indicate in weather observation?

The correct answer is A, which stands for "No Significant Cloud." In weather observations, NSC is a term used by meteorologists and air traffic control to indicate that there are no significant clouds that would impact visibility, flight safety, or weather conditions for aviation purposes. This designation is important for pilots and air traffic controllers to understand the state of the atmosphere and make informed decisions regarding flight operations.

By indicating that there are no significant clouds, NSC helps to assure pilots that they are likely to encounter good flying conditions without the complications associated with cloud cover, such as turbulence or limited visibility. Thus, NSC conveys essential information about current weather conditions, aiding in the safety and efficiency of air travel.