Which of the following indicates a valid permanent SAS data set?

A permanent SAS data set is one that is stored on disk and persists beyond the current SAS session, while a temporary data set is stored in the Work library, which is cleared at the end of a session.

In the context of SAS, data sets residing in the Work library are temporary and lose all stored information once the SAS session ends. The naming convention typically follows the pattern of library name followed by dataset name (e.g., library.dataset).

In the choices provided, "Work.ptdt" is a typical representation of a temporary data set, as it explicitly references the Work library. "Temporary.ptdt" would also refer to a temporary data set since it indicates the temporary library. The choice simply stating "ptdt" does not indicate which library it belongs to, but if no library is specified, it defaults to Work, which is still temporary.

The correct assessment concludes that none of the options represent a valid permanent SAS data set, leading to the conclusion that the correct answer is indeed that none of the above represent permanent data sets. This is how it aligns with the definitions of SAS data set persistence and storage.