【TPO5】mineral and plants 第11题第三选项不懂。求解。

dufresnewan

原文 第六段 如下
【Paragraph 6】Only recently have investigators consideredusing these plants to clean up soil and waste sites that have been contaminatedby toxic levels of heavy metals–an environmentally friendly approach known asphytoremediation. This scenario begins with the planting of hyperaccumulatingspecies in the target area, such as an abandoned mine or an irrigation pond contaminated by runoff. Toxic mineralswould first be absorbed by roots but later relocated to the stem and leaves. Aharvest of the shoots would remove the toxic compounds off site to be burned orcomposted to recover the metal for industrial uses. After several years ofcultivation and harvest, the site would be restored at a cost much lower thanthe price of excavation and reburial, the standard practice for remediation ofcontaminated soils. For examples, in field trials, the plant alpine pennycressremoved zinc and cadmium from soils near a zinc smelter, and Indian mustard, native to Pakistan andIndia, has been effective in reducing levels of selenium salts by 50 percent incontaminated soils.


11. It can beinferred from paragraph 6 that compared with standard practices for remediation ofcontaminated soils, phytoremediation

○does not allow forthe use of the removed minerals for industrial purposes

○can be faster toimplement

○is equallyfriendly to the environment

○is less suitablefor soils that need to be used within a short period of time

根据第二行an environmentally friendly approach known as phytoremediation，不能推断出选3么？

求解，谢谢各位！