The destruction of habitats(栖息地)all over the world is the primar

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
【正确答案】：D
【题目解析】：在第28题中，我们需要找到一个词来描述由于各种污染源（如城市污水和农场化学径流）而改变的水流中的“____”和数量。 A. Amount（数量）：虽然文中提到了“quantity of water”（水的数量），但“amount”和“quantity”在含义上有所重叠，且“amount”通常用于描述不可数名词的总量，不太符合此处描述水流特性的语境。 B. purity（纯度）：虽然水源的纯度确实是一个重要的考虑因素，但文中强调的是由于污染导致的改变，而不是单纯地描述水的纯净度。 C. nature（性质）：虽然“nature”可以用来描述事物的本质或特性，但在此上下文中，它并不直接对应由于污染而改变的水的特性。 D. quality（质量）：这个词在此处最合适，因为它可以涵盖水的各种特性，包括清洁度、可饮用性以及其他由污染可能引起的变化。此外，文中提到的各种污染源可能会改变水的“quality and quantity”（质量和数量），这进一步支持了选择“quality”作为正确答案的理由。 因此，第28题的答案是D，即“quality”。