TOEFL Reading: ETS-TOEFL阅读机经 - KXP79I7Z2Y33JUW1L$

All of the following are mentioned in paragraph 2 as operations involved in the Mesopotamian irrigation system EXCEPT A. determining how much irrigation water should be distributed to various farmers B. widening existing canals so they could hold more water C. removing undesirable materials from the intakes of irrigation canals D. building new canals so irrigation water could be transported to distant areas