What are the common prefixes indicating cloud elevation?

The correct response identifies the prefixes "Cirro" and "Alto" as common indicators of cloud elevation. In meteorology, "Cirro" refers to high-altitude clouds that typically form above 20,000 feet (6,000 meters). These clouds are often thin and wispy, indicating they are composed of ice crystals. Examples include cirrus and cirrostratus clouds.

On the other hand, "Alto" signifies mid-level clouds, which generally form between 6,500 to 20,000 feet (2,000 to 6,000 meters). These clouds appear more substantial than cirrus clouds but are not as dense as low-level clouds. Examples include altostratus and altocumulus clouds.

The other prefixes described in the other choices do not consistently indicate cloud elevation in the same way. For example, "Nimbo" typically implies precipitation, often associated with low-level clouds like nimbostratus, but it does not provide specific information regarding cloud elevation. Therefore, "Cirro" and "Alto" remain the standard prefixes for identifying high and mid-level clouds respectively, making this the correct choice.