Explanation:

- The first book in which the transactions of a business unit are recorded is known as the "book of original entry."

- Option 1: Balance Sheet - This is a financial statement showing a company's financial position, not used for initial transaction recording.

- Option 2: Cash Book - A specialized journal that records only cash transactions, not where all initial entries are made.

- Option 3: Ledger - Compiles information from journals, not the first place of entry.

- Option 4: Journal - Known as the book of original entry, where all business transactions are first recorded sequentially. Correct Answer