Classify the following controls as preventive, detective, or corrective:

Periodic bank reconciliation.

Separation of cash and accounting records.

Maintaining backup copies of master and transaction files.

Pre-numbering of sales invoices.

Chart of accounts.

Retina scan before entering a sensitive R & D facility.

Resubmission of transactions for subsequent processing.

Internal auditor rechecking the debits and credits on the payment voucher.

Depositing all cash receipts intact.

Qualified accounting personnel.