C is corrent because factoring is the term used for the sale of accounts receivable.
A is incorrect because collateralizing is a term not normally used for methods of financing receivables.
B is incorrect because assigning does not result in a sale of receivables. It is a method of providing security to obtain financing.
D is incorrect because pledging does not result in a sale of accounts receivable. It is a method of providing security to obtain financing.
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