Final answer:
The correct statement about T-accounts is that they are summary devices with credits posted on the right side of the vertical line.
Step-by-step explanation:
Regarding T-accounts, the correct statement is that a T-account is a summary device with credits posted on the right side of the vertical line. Statement D is accurate as the structure of a T-account includes a two-column format resembling the letter 'T', where the left side represents debits for asset accounts and increases in expense accounts, and the right side signifies credits for liability or equity accounts and revenue increases. The fundamental concept behind the T-account in accounting is that it visually separates different types of transactions and helps in understanding the flow of transactions within a business.