TOEFL Reading: ETS-TOEFL阅读机经 - 8D3VEZH5Z738374KL$

According to paragraph 6, oneway grazing contributes to maintaining high natural plant diversity of grasslands is by A. controlling how fast nutrients leave the soil B. guaranteeing that enough sunlight is given to low-growing plants C. allowing tall plant species to compete for space D. improving the distribution of the plants with the highest productivity throughout grassland areas