Answer:
C. Railroad owners gave secret discounts to their biggest customers.
Explanation:
Rebate is the refund given to the customer after he had paid the price of a product. Its use was widespread among large industrialists during 19th century undercutting the competition. Customers were granted rebate in secret. Rebates were also used by railroad companies for price discrimination, the companies used to give small rebate to secure large freight orders. The standard oil company established its monopoly by using rebate method.
