11．They have no brains and no spines （脊椎）．You can often see right through them．But they can cause painful，sometimes deadly stings （刺伤）．Some can even glow in the dark!Scientists know them as medusas，but most people call them jellyfish．
Jellyfish are not really fish．Jellyfish have stomachs and mouths，but no heads．They have nervous systems for sensing the world around them．They are made almost entirely of water，which is why you can look through them．Most jellyfish live in salt water，apart from a few types that live in fresh water．Jellyfish are found in oceans and seas al over the world．They live in warm，tropical seas and in ice waters near the North and South Poles．
Adult jellyfish are shaped like an open umbrella or a bell．A Jellyfish has tentacles （触须） at the edges of its body．At the center of a jellyfish's body，where it is widest，is the mouth．The ends of the tentacles have sting cells on them，which jellyfish use to catch their prey （猎物）．Some jellyfish have powerful stings that can kill people．
Most jellyfish eat fish，tiny creatures and even other jellyfish．Once a jellyfish stings and catches its prey，it takes the prey to its mouth and swallows it．
Some jellyfish are very small，no longer than a marble （弹子）．Others are quite large．The largest jellyfish can grow to about 7feet （about 2meters） across and weight hundreds of pounds!Jellyfish may be blue，orange，pink，yellow，purple，and other colors．
Some jellyfish can glow in the dark by making their own light．The light is made by a chemical reaction inside the jellyfish．Scientists believe jellyfish glow for several reasons．For example，they may glow to attract animals they prey on．
24．What is the second paragraph mainly about？D
A．What jellyfish live on．
B．What jellyfish look like．
C．How jellyfish move．
D．What jellyfish are．
25．What is in the center of a jellyfish's body？B
A．Its brain．
B．Its mouth．
C．Its nervous system．
D．Its stomach．
26．How does a jellyfish catch and eat its prey？C
A．It stings and catches its prey，then sends it into its mouth to chew it．
B．It bites the prey with its mouth，chews it with its teeth and then swallows it．
C．It stings the prey with its tentacles and then swallows it directly．
D．It tears the prey into small pieces and sends it into its mouth to swallow it．
27．What can we learn from the text？A
A．Some jellyfish can make a person die．
B．Most jellyfish live in fresh water．
C．Most jellyfish can be planted in the ocean．
D．Jellyfish only have five colors．
分析 本文是一篇说明文．主要介绍了水母的相关内容．水母不是一种鱼，而是一种可以致人死亡的海洋生物．
解答 24．D 主旨大意题．根据文章第一段They have no brains and no spines （脊椎）．You can often see right through them．Jellyfish are not really fish．以及第二段第一句"Jellyfish are not really fish．"就可以看出本段主要介绍了"什么是水母"．故选D．
25．B 细节理解题．由第三段第三句"At the center of a jellyfish's body，where it is widest，is the mouth．"可知在水母身体的中央是其嘴巴．故选B．
26．C 细节理解题．由第三段最后一句"The ends of the tentacles have stinging cells on them，which jellyfish use to paralyze and catch their prey．"及第四段第二句"Once a jellyfish stings and paralyzes its prey，it takes the prey to its mouth and swallows it．"可知水母通过触须的终端刺伤猎物，然后送进嘴里后直接吞掉，故C项正确．
27．A 推理判断题．由第一段第三句"But they can cause painful，sometimes deadly stings．"可知一些水母甚至能让人死亡．故选A．
点评 本文是科教类阅读理解．做这类题材阅读理解时要求考生对文章通读一遍，做题时结合原文和题目有针对性的找出相关语句进行仔细分析，结合选项选出正确答案．推理判断题也是要在抓住关键句子的基础上合理的分析才能得出正确答案，切忌胡乱猜测，一定要做到有理有据
