TOEFL Reading: ETS-TOEFL阅读机经 - 073WYVQY6U1M737QL$

According to paragraph 2, what happened as urban areas matured? A. Urban areas became increasingly dependent on grain produced in distant areas. B. Urban areas began to rely on their own stored surpluses of wheat flour. C. Urban consumers were forced to reduce their consumption of grain by one fourth. D. Urban areas relied more on rice and less on wheat.