Which of the Following Is the Best Definition of Operating

Which of the following is the best definition of operating cycle?

A) A written statement by a bank that money will be paid, provided conditions specified in the letter are met.
B) Short-term financing in which the factor purchases all of a firm's receivables and forwards the proceeds to the seller as soon as they are collected.
C) The time period between the acquisition of inventory and when cash is collected from receivables.
D) Loan negotiated with banks for day-to-day operations.
E) Costs that fall with increases in the level of investment in current assets.