A consultant is preparing to enable multicurrency in an org that already has active pricing...

Comprehensive and Detailed Explanation From Exact Extract:

For Revenue Cloud’s Salesforce Pricing:

The Currency field becomes available for use in decision tables and pricing procedures only after multicurrency is enabled.

If a decision table and pricing procedure are already active, you must deactivate them, update the table to include Currency, and then reactivate.

Simply waiting (C) will not retroactively expose Currency in existing decision tables. Cloning (A) is unnecessary and more complex than required.