If you have a Usd.

The correct method is my_prim.GetAttribute("size") because the question asks for a specific attribute , not a relationship or generic property. NVIDIA’s Learn OpenUSD material defines properties as the data-bearing namespace objects on prims and distinguishes two property categories: attributes and relationships . Attributes hold typed values, while relationships point to other objects in the scene description. NVIDIA’s Omniverse developer reference also states that Usd.Prim.GetAttribute() returns a Usd.Attribute, after which Usd.Attribute.Get() is used to resolve the actual authored or composed value.

Option A is therefore the precise API call. Option B is incorrect because GetRelationship() retrieves relationship properties, not value-bearing attributes. Option C is less specific: GetProperty("size") can retrieve either an attribute or relationship as a generic UsdProperty, requiring additional type handling. Option D is incorrect because primvars are accessed through schema-specific APIs such as UsdGeom.PrimvarsAPI, not directly as a general Usd.Prim method. This aligns with Pipeline Development → USD Python API, Property Access, Attributes, Relationships, and Scenegraph Authoring .