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：

★ 山西省永济市涑北中学高三英语总复习：美文欣赏（2）（Invitation）

★ 【优化方案】2017届高考英语二轮复习全国卷Ⅱ题型重组训练：第12组（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年高考英语二轮复习精品资料：专题15 完形填空（押题专练）（原卷版）

★ 【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）

★ 2017届高考英语二轮复习书面表达限时测验：5（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

★ 2017届高考英语二轮复习课时训练：8（含解析）

★ 2017届高考英语二轮复习课时训练：4（含解析）

★ 2014届高考英语一轮复习课时作业(三)必修1Module 3《My First Ride on a Train》（外研版）