单选题
In his 1979 book, The Sinking Ark, biologist Norman Myers estimated that (1) of more than 100 human-caused extinctions occur each clay, and that one million species (2) by the century's end. Yet there is little evidence of (3) that number of extinctions. For example, only seven species on the (4) species list have become extinct (5) the list was created in 1973. Bio- (6) is an important value, according to many scientists. Nevertheless, the supposed mass extinction rates bandied about are (7) by multiplying (8) by improbables to get imponderables. Many estimates, for instance, rely a great deal on a "species-area (9) ", which predicts that twice as many species will be found on 100 square miles (10) on ten square miles. The problem is that species are not distributed (11) , so bow much of a forest are destroyed may be as important as (12) . (13) , says Ariel Lugo, director of the International Institute of Tropical Forestry in Puerto Rico, "Biologists who predict high (14) rates (15) the resiliency of nature". One of the main muses of extinctions is deforestation. According to the Consultative Group on International Agricultural Research, what destroys tropical trees is not commercial logging, (16) "poor farmers who have no other (17) for feeding their families than slashing and burning a (18) of forest". In countries that practice modern (19) agriculture, forests are in (20) danger. In 1920, U. S. forests covered 732 million acres. Today they cover 737 million.
【正确答案】
A
【答案解析】an average平均数。number数字；sum总数，金额；amount数量。a sum of意为“一笔”，一般后面接金钱，也可接其他不可数名词。an amount of意为“许多”，后接不可数名词。根据后面出现的each day可以确定应用an average。句意：生物学家诺曼•迈尔斯在其1979年所著的《正在沉没的方舟》中估计每天人为原因造成的物种灭绝超过100种，到本世纪末会有100万个物种灭绝。
【正确答案】
B
【答案解析】would disappear。语法测试点为过去将来时。这个句子中that one million species…是estimated的宾语从句。主句动词用一般过去时，宾语从句中表示将来的动词应用过去将来时。很多同学误选[D]，注意此处不是虚拟语气。
【正确答案】
A
【答案解析】any where near接近于。little表示否定，可排除“somewhere near”和“something like”。anywhere可以表示数量不确定，大概在…之间，故A项正确，这里是指数量上的关系，而不是时间的关系，因此不能用anytime when。句意：不过并没有什么证据表明已灭绝的物种接近这个数目。
【答案解析】In addition另外。语篇关系题，上一段谈到一个问题，这一段又谈到另外一个问题，因此应用表示补充说明的关联词。But但是；Instead代替，而是；As a result结果，因此。句意：另外，波多黎各热带森林研究所主任阿莱尔·卢戈还说，生物学家高估物种灭绝速度的同时也低估了自然界的恢复力。