I go for E.
conclusion: this approach may in fact make things worse rather than better
Premises: 1) Manatees got killed if swimming close to surface
2) to resolve this, low down speed
3) Manatees cannot hear low-pitched voice
weaken? you wanna find an answer that proves the approach doesnt not worsen the problem.
B: 海牛的食物适于在静水中生长,船开得快会破坏其生长环境. ==> it is "still water". lower speed doesnt mean the water will be still. the end result might be the same because, after all, water is not still.
E: 给海牛放各种速度船的录音,它们根本不能将船的声音与背景噪音中区分开来。即船速快慢,噪音大小对海牛都一样 ==> this proves the approach doesnt contribute, either positively or negatively, to the problem. therefore, weaken the conclusion...
hope it helps.
-- by 会员 chasingM7 (2011/8/18 17:43:13)