Which archival method moves from the largest and most general to the smallest and most specific?

The question asks for the method that assists with archival organization and description by moving from the largest and most general to the smallest and most specific.

• a. Level of description: This refers to the hierarchical approach used in archival description. Archivists describe records at various levels, starting with the broadest (e.g., the entire collection or fonds), then moving to more specific levels (e.g., series, sub-series, files, and individual items). This process directly matches the description of moving from the largest and most general to the smallest and most specific.
• b. Level of arrangement: This refers to the physical and intellectual organization of the records themselves, not primarily the description of them.
• c. Levels of organization: This is a broader term that could include arrangement and description, but "level of description" is the precise term for the hierarchical descriptive process.
• d. Respect des fonds: This is a core archival principle that dictates that records created by a particular agency or person should be kept together and not mixed with records from other sources. It's about maintaining provenance and original order, not the hierarchical description.

Therefore, "Level of description" is the method that involves archival description from the largest and most general to the smallest and specific.

The final answer is $\boxed{\text{a. Level of description}}$.