托福阅读句子插入题16

　　托福阅读中句子插入题是重要题型之一。根据托福阅读题型不同来进行专项练习，是短期提高托福阅读能力的有效方法。同学们需要多加练习哦!

　　托福阅读句子插入题：The Cambrian Explosion

　　【Paragraph 3】One interpretation regarding the absence of fossils during this important 100-million-year period is　that early animals were soft bodied and simply did not fossilize. ■Fossilization of soft-bodied animals is less likely than　fossilization of hard-bodied animals, but it does occur. ■Conditions that promote fossilization of soft-bodied animals　include very rapid covering by sediments that create an environment that discourages decomposition. ■In fact, fossil beds containing soft-bodied animals have been known for many years. ■(The Cambrian Explosion)

　　Look at the four squares [■] that indicate where the following sentence could be added to the passage.It is relatively

　　rare because the fossilization of soft-bodied animals requires a special environment.

　　Where could the sentence best fit?