TOEFL Reading: ETS-TOEFL阅读机经 - RA1LQ8S2E58DV9I9L$

According to paragraph 5, one of the main reasons for using legumes in crop rotation is that legumes A. have no serious insect pests B. cover the soil more completely than any other crop does C. build up the nitrogen content of the soil D. are very easy to plant in strips