Considering the two files cars.

The missing chassis is caused by an unresolved reference target. In parkingLot.usda, the reference is authored as @cars.usda@ without a target prim path. When a reference omits the target prim path, USD uses the referenced layer’s defaultPrim as the entry point. NVIDIA’s Learn OpenUSD guide states that if no defaultPrim is set, bringing that layer in as a reference or payload resolves as an empty layer and emits a warning. It also identifies defaultPrim as layer metadata and a best practice for stages intended to be referenced or payloaded.

Option A fixes the issue by setting, for example, defaultPrim = "redCar" in cars.usda, allowing @cars.usda@ to resolve to /redCar and bring in its chassis. Option C also fixes it by making the reference explicit, for example references = @cars.usda@ < /redCar > . NVIDIA’s data-transformation guidance similarly notes that without defaultPrim, a stage cannot be referenced without specifying a target prim. Option B does not solve reference resolution; assigning a type to car01 would not identify which car to compose. Option D changes model-kind semantics only and does not affect the reference target. This aligns with Composition → References, Default Prim, Target Prim Paths, and Asset Entry Points .