托福阅读重点考察考生的阅读理解和对于信息提取的能力，是为将来进一步的学术期刊的阅读和学术研究打下基础。阅读文章中出现的长难句常是考生阅读中遇到的一大难点，而托福阅读十种题型中的句子简化题更是针对文章中的长难句进行了重点考察。
At one time， the animals present in these fossil beds were assigned to various modern animal groups， but most paleontologists now agree that all Tommotian fossils represent unique body forms that arose in the early Cambrianperiod and disappeared before the end of the period， leaving no descendants in modern animal groups.animals found in the Tommotian fossil bed were once thought tobelong to a variety of modern animal groups， but now they are thought to have descended from a single group.
Animals in the Tommotian fossil beds were initially assigned tomodern animal groups but are now thought to belong to groups that emerged and died out during the Cambrian period.
Though at first they thought otherwise， paleontologists now agree that the animals in the Tommotian have body forms from which modern animals have descended.
It is unclear whether the Tommotian fossils from the early Cambrianperiod represent unique body forms or whether they should be assigned to various modern animal groups.
解题：
1看原句是否有逻辑关系词
浏览原句，发现有but这个表转折的逻辑词。
该句句意：曾经，存在于这些化石中的动物被规定为现代动物种群，但是，如今，考古生物学家认为所有的Tommotian化石代表独有的个体，它们起源于寒武纪初期，并消失于该纪元的末期，导致该动物种群在现代动物种群中没有留下后代。
2看选项表达转折关系的逻辑词
A选项有but
B选项有but
C选项是although表让步转折
D选项是没有逻辑关系的复合句
D选项首先排除。
3细节对比解题
在A，B，C三选项中，
A选项句意：在Tommotian化石床中发现的动物曾被认为属于现代动物种群，但是现在，它们被认为是单一动物种群的后代。
显然，但是后的内容与原句但是后的内容完全不符。
B选项句意：在Tommotian化石床中发现的动物最初被规定为现代动物种群，但是现在被认为属于出现于寒武纪初期，灭绝于寒武纪末期的动物种群。
B选项但是前后的内容和原句但是前后的内容完全吻合。
看到这里就把B选了吧，其它选项看了是浪费时间，况且是胡编乱造的，影响对文章的理解。
