What device is used to record changes in fundamental accounting elements?

The correct choice is an account, which is a fundamental component in accounting that is used to record the financial transactions regarding a specific item. An account maintains a running total of financial activities related to that item, providing a continual record of changes over time. This tracking allows for monitoring increases and decreases in value, such as assets, liabilities, equity, revenues, and expenses, hence reflecting changes in the fundamental accounting elements.

In contrast, a journal serves as an initial recording point for transactions before they are entered into accounts, making it more of a chronological log rather than a detailed tracking device for specific items. A ledger, which is composed of several accounts, organizes the information from the journal. While it aggregates data, it does not serve the same primary purpose as an individual account does in recording changes. A transaction book is not a standard accounting tool but could refer to a record of transactions without the specific structural function of an account.