Final answer:
The informal format used for problem-solving accounting transactions is the T-account, a tool represented by a simple two-column balance sheet showing 'Assets' and 'Liabilities'. Hence, the correct answer is option (A).
Step-by-step explanation:
The format that provides an informal view of account activity and is used for problem-solving accounting transactions is a T-account. A T-account is essentially a balance sheet with a two-column format. This format becomes recognizable by the T-shape formed by the vertical line down the middle and the horizontal line under the column headings for “Assets” and “Liabilities”.
It offers a simple and clear visualization of the debits and credits affecting individual accounts, making it a helpful tool for understanding and solving accounting problems. Therefore, the correct answer to the question is A. T-account.