To become transparent, an animal needs to keep its body from absorbing or scattering light. Living materials can stop light because they contain pigments(色素) that absorb specific colors of light. But a transparent animal doesn’t have pigments, so its tissues won’t absorb light. According to Johnsen, avoiding absorption is actually easy. The real challenge is preventing light from scattering.

　　Animals are built of many different materials----skin, fat, and more----and light moves through each at a different speed. Every time light moves into a material with a new speed, it bends and scatters. Transparent animals use different tricks to fight scattering. Some animals are simply very small or extremely flat. Without much tissue to scatter light, it is easier to be see—through. Others build a large, clear mass of non-living jelly-lie(果冻状的)material and spread themselves over it .

　　Larger transparent animals have the biggest challenge, because they have to make all the different tissues in their bodies slow down light exactly as much as water does. They need to look uniform. But how they’re doing it is still unknown. One thing is clear for these larger animals, staying transparent is an active process. When they die, they turn a non-transparent milky white.

　　21.According to Paragraph 1, transparent animals_______.

　　A. stay in groups

　　B. can be easily damaged

【2016届高三英语二轮复习作业卷：22（含解析）（河北衡水）】相关文章：

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题12 人物类话题指导（教师版）

★ （安徽专用）2014届高考英语一轮复习方案 作业手册（10）模块4 《Unit 10 Money》（含解析） 北师大版必修1

★ 2017届高考英语二轮复习课时训练：11（含解析）

★ 2017届高考英语二轮复习课时训练：8（含解析）

★ 【课堂新坐标】2017届高考英语（通用版）二轮复习书面表达专题训练：技法6 规避重复适当进行句式升级（含解析）

★ 2017届高考英语二轮复习课时训练：12（含解析）

★ 2017高考四川省广安市英语阅读理解一轮系列训练：20（含解析）

★ 2017届高考英语二轮复习课时训练：4（含解析）

★ 北京市2014高考英语一轮复习 练习手册（31）选修7 Unit 1 Living well（含解析）新人教版

★ 【优化方案】2017届高考英语二轮复习全国卷Ⅱ规范练：4（含解析）