TOEFL Reading: ETS-TOEFL阅读机经 - TA144AEM4Z79M5QIL$

According to paragraph 4, which of the following is true of the more-likely-used solutions to the problem of salinization? A. They resulted in a decrease in the amount of food that was produced. B. They succeeded only on areas where the natural water table was especially low. C. They often demanded much time and effort on the part of their users. D. They often led to other technological advances.