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21题的答案是（ ）
A、landscapes
B、cities
C、maps
D、pictures
【正确答案】：A
【题目解析】：第21题要求从给定的选项中选择一个词来填空，使句子意思完整且逻辑通顺。句子是：“Houses, highways, dams, industrial buildings, and ever-spreading farms now dominate _______ formerly occupied by forests, deserts, and wetlands.” 在这个句子中，需要找到一个词来描述那些曾经被森林、沙漠和湿地占据的地方现在被什么所占据。选项A“landscapes”（风景，地貌）是最合适的，因为它涵盖了房屋、公路、大坝、工业建筑和不断扩展的农场等现在占据的这些地区，而且“landscape”通常用于描述自然或人为形成的广阔地理区域的整体特征。 选项B“cities”（城市）太过局限，因为句子中提到了除了城市之外的其他许多类型的人工构造，比如公路和大坝。选项C“maps”（地图）和选项D“pictures”（图片）都与句子描述的现实世界的改变无关。 因此，选择A“landscapes”作为第21题的答案是合适的。