The correct answer is C. Group.
A ledger is a book of accounts that contains all the financial transactions of a business. A group of ledgers of the same nature is called a ledger group. For example, a company may have a ledger group for all its sales transactions, a ledger group for all its purchases transactions, and a ledger group for all its payroll transactions.
A voucher is a document that supports a financial transaction. For example, a sales invoice is a voucher that supports a sale. An asset is a resource that a company owns and expects to benefit from in the future. For example, a company’s inventory is an asset.
None of these is the correct answer because it does not describe a collection of ledgers of the same nature.