Final answer:
The DG - Donation Gain transaction reason is used to properly establish accountability for donated medical equipment.
Step-by-step explanation:
The Inventory Gain Equipment transaction reason that is used to properly establish accountability for donated medical equipment is option B) DG - Donation Gain. This transaction reason is specifically designed for recording the gain in inventory when medical equipment is received as a donation. By selecting this transaction reason, the organization can accurately track and account for the value of donated medical equipment in their inventory system.