Final answer:
The most likely reason for the 136 orders still not being invoiced is human error in data entry.
Step-by-step explanation:
The most likely reason for the 136 orders still not being invoiced after appending data for missing orders to the invoices table is D) Human error in data entry. Human error in data entry can result in missing orders not being properly recorded in the system, leading to the discrepancy. For example, if a data entry clerk accidentally skips entering the order details or makes a mistake while entering the customer information, it can result in orders not being invoiced.
It is important for businesses to have strong data entry processes in place and implement proper checks and controls to minimize the occurrence of human errors. Regular audits and validations can also help identify and rectify any errors in the invoicing process.
Therefore, the most likely reason for the 136 orders still not being invoiced is human error in data entry.