TOEFL Reading: ETS-TOEFL阅读机经 - 00T47FB8CF_GC34ML$

Which of the following is NOT mentioned in paragraph 4 as a way that English landlords tried to increase the efficiency of their farms? A. encouraging the use of methods as crop rotation B. selecting crops on the basis of demand in the London market C. increasing rents and reducing the length of phases D. hiring Yeomen to work on their farms instead of relying on tenants