TOEFL Reading: ETS-TOEFL阅读机经 - T46K5C2OQYW00YU5L$

According to paragraph 1, a major disadvantage of cereals is that they A. cannot be used as animal food B. must be planted in a different field every year C. take a long time to ripen before they can be used or stored D. use up all of the nitrogen in a field unless fertilizer is used