TOEFL Reading: ETS-TOEFL阅读机经 - Z1EQMY4785O3445AL$

According to paragraph 6, what is true about the quantities of commercial inorganic fertilizers used globally? A. They are likely to drop by about 40% in the next ten years. B. They have increased at a steady rate since 1950. C. They increased during the 1990s, but at a slower rate than over the previous 40 years. D. They dropped during the 1990s after having risen sharply over the previous 40 years.