Standard FAR part 52 clauses and provisions sometimes end with interchangeable paragraphs called:

Substitutes refer to alternatives or replacements for items or services specified in a contract, but they do not relate specifically to the interchangeable paragraphs found in FAR clauses. While substitutes may be applicable in various contexts, they do not encompass the interchangeable nature of paragraphs within FAR part 52 clauses.

Amendments are formal changes made to existing contracts, modifying terms, conditions, or provisions. While amendments can affect clauses and provisions, they do not represent the interchangeable paragraphs that are designed to provide options within the original text of FAR part 52 clauses.

Interchangeables is not a recognized term in the context of FAR part 52 clauses. While it may suggest the idea of elements that can be swapped, the proper terminology used in FAR to describe interchangeable paragraphs is "Alternates," making this choice incorrect.