Which of these data is lost when flattening a stage?

Flattening a stage resolves the composed result into a single merged layer, baking the effects of composition into authored scene description. The critical loss here is variant-set structure . OpenUSD’s UsdStage::Flatten() documentation states that flattening removes most composition metadata and that “all VariantSets are removed and only the currently selected variants will be present in the resulting layer.” This means the flattened output preserves the currently selected representation, but the ability to switch among alternate variants is lost.

Option C is therefore correct. Option A is not the best answer because flattening authors resolved values and can preserve relevant composed metadata, although composition metadata is removed. Option B is incorrect because modern OpenUSD flattening preserves native scenegraph instancing by flattening prototypes and adding internal references from instances to their corresponding prototypes. Option D is incorrect because class prims still exist after flattening, although inherit arcs are removed and inherited data is copied onto consuming prims. This aligns with Composition → Flattening, Variant Sets, Composition Metadata, Inherits, and Scenegraph Instancing .