[单选题]The destruction of habitats(栖息地)all over the world is the primary reason species are?becoming extinct(灭绝)or endangered．Houses,highways,dams,industrial buildings,and?ever-spreading farms now dominate?21?formerly occupied by forests,deserts,and wetlands．22?the beginning of European settlement in America,23, over 65,000,000 acres of?wetlands have been drained．One million acres alone vanished 24?1985 and 1995． Habitat destruction can be?25?or it can be subtle,occurring over a 26?period of time?without being noticed．27?such as sewage from cities and chemical runoff fromfarms,can change?the?28?and quantity of water in streams and rivers．To?29?living in a delicately balanced?habitat,this disturbance can be as 30?as the clear-cutting of a rainforest． 31?remaining habitats are carved into smaller and smaller pockets or islands,remaining?species are forced to exist in these?32?areas,which causes further habitat?33?These?species become less adaptable to environmental?34；in fact,they become?35?endangered．Scientists believe that when a habitat is cut by 90%,one-half of its plants,animals and insects will?become extinct． 第28题的答案是（ ）
A.Amount
B.purity
C.nature
D.quality

最新试题

• ●    利率是各国调整国民经济的杠杆之一，其高低首先取决于（）。
• ●    患者，女性，32岁，重症肌无力患者，近2个月症状渐加重，出现四肢无力，进食费力和饮水呛咳，但无呼吸困
• ●    [判断题]干旱或半干旱地区冲积扇泥质沉积物一般为褐色,含钙质结核。
• ●    [单选题]GB3847.2018 中要求,加载减速检测中,如果环境温度超过( )℃应终止检测
• ●    [判断题]担当救援的动车组司机接到救援命令后，必须认真确认。命令不清、原因不明确时，不准动车。（
• ●    [单选题]深基坑工程为开挖深度超过（ ）的基坑（槽）的土方开挖、支护、降水工程。