Which of the following is not a component of clasp assembly?
A clasp assembly should consist of four component parts. First, one or more minor connectors should be present, from which the clasp components originate. Second, a principal rest should be designed to direct stress along the long axis of the tooth. Third, a retentive arm should engage a tooth undercut. For most clasps, the retentive region is only at its terminus. Fourth, a nonretentive arm (or other component) should be present on the opposite side of the tooth for stabilization and reciprocation against horizontal movement of the prosthesis (rigidity of this clasp arm is essential to its purpose).
Key Concept:
Rest seat: The prepared recess in a tooth or restoration created to receive the occlusal, incisal, cingulum, or lingual rest. There should be a principal rest, as a component of RPD  designed to direct stress along the long axis of the tooth.
Note: Out of the given options, rest seat is not a component of RPD.
Ref: McCrackens Removable Partial Denture Ed13th Pg 71
Minor connector
Retentive arm
Rest seat
Reciprocal arm