多选题 By ______ many aspects of natural river ecosystems, some dams cause serious harm, producing ______ effects on water, land, wildlife, and even the atmosphere.
【正确答案】 B、F
【答案解析】[解析] ● 逗号说明前后同义重复。
● 第三空与harm(伤害)同义重复。negligible可忽略的，salutary有利的，deleterious有害的。答案选F。
● obliterate除去，alter变更，ameliorate改善。代入选项，答案选B。