問題詳情

Questions 10-18Some people are concerned that our soils arc becoming depleted of trace minerals by continuous agricultural use and hence that foocte are becoming depleted in vital minerals.This is a complex issue about which not a great deal is known, but the lack of evidence ofLine mineral deficiencies in our population speaks to the adequacy of our soils. Furthermore,5 soils are replenished in trace minerals by rainwater and especially by irrigation water thatis obtained from rivers or wells that draw water from other soil or rock formations faraway from the farm,On the other hand, agricultural practices that remove the total crop from the field yearafter year with no replenishment of trace minerals can over time result in a crop poor in10 these minerals. Of course, the fanner could supply chemical fertilizer to the fields* butwith most fertilizers this practice would replenish only potassium, phosphates, and nitrogen. Rotating a "green manure" crop such as clover, which is plowed under after the end of thegrowing season, would renew only nitrogen in the soil, not trace elements. There is agrowing realization, therefore, (hat so-called organic farming makes good commercial15 sense and would help minimize mineral depletion: Organic fanning essentially refers to farming that does not depend on chemical fertilizers; rather, soils are invigorated byapplying manure and by plowing in crop wastes, such as corn stalks and bean vines, and compost. These techniques return organic material and trace minerals back to the soils andare to be commended. However, for maximum yields, a chemical fertilizer may be required20 in addition to manure and plant waste.Some critics of modern farming methods fear that the hardier varieties of fruits andvegetables that have been developed to make shipment easier have resulted in loss ofvitamin content. This concern is unfounded because the creation of vitamins by plants isan automatic biological process. Any variety of plant will make the full complementof vitamins it needs, regardless of species.
10. The word "vital" in line 2 is closest in meaning to
(A) effective
(B) ideal
(C) unique
(D) necessary

參考答案

答案：D
難度：適中0.681319
統計：A(11),B(7),C(10),D(62),E(0)

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