Concept: A vending machine is an automated retail device that completes sales without a human sales attendant.
Explanation: A vending machine is designed to accept payments from customers.
Once a customer slots in money and selects a product, the machine releases that product automatically.
It checks the amount paid against the product price before dispensing the item.
Because the whole process is self-service, no attendant is needed for the sale.
Such machines are often used for snacks, drinks, or tickets in public areas.
In contrast, a telex machine and a fax machine are used for message transmission, not direct retail sales.
A computer machine cannot physically dispense goods without other equipment.
Therefore, the only option that matches the description is the vending machine.
Answer: C. Vending Machine