What is the correct shape-based difference between stratus and cumulus clouds?

Correct answer: Stratus are layered and cumulus are heap-like

Cloud shape helps us distinguish major cloud types. Stratus clouds spread across the sky in broad, fairly uniform layers, often making the sky look covered. Cumulus clouds develop as separate, rounded, puffy masses that resemble heaps or cotton-like piles. Thus, the important contrast is between a sheet-like form and a heap-like form. The other choices confuse clouds with forms of precipitation, visibility conditions, or frost, so they do not describe cloud shape.

Option A is correct because it gives the standard shape-based distinction: stratus are layered, while cumulus are heap-like or piled up. This distinction describes appearance, not necessarily the weather produced by every cloud. A cumulus cloud may grow tall, and a stratus cloud may be associated with dull weather, but those facts are not needed here. Remembering “stratus = spread-out layer” and “cumulus = separate heap” makes the answer clear.