TOEFL Reading: ETS-TOEFL阅读机经 - F0N4L46GH2P162Z5L$

According to paragraph 5, a custom mill became a merchant mill by A. agreeing to sell grain to the state government at a reduced price B. providing goods to fulfill the demand of traders in the main port cities C. limiting the amount of work a mill would do for individual farmers to only a few days a week D. hiring specialized millers to produce each type of flour