D．improve the environment of bluefin tuna

　　解析：选C　细节理解题。由倒数第四段中的"To prevent extinction, they say limits must be placed on fisheries"和倒数第三段中的"we need to reduce the number of catches of young fish to improve the species' situation"可知，要防止太平洋蓝鳍金枪鱼灭绝，必须限制捕捞，减少幼鱼的捕量。

　　4．What would be the best title for the text?

　　A．Fish at risk

　　B．Species on the Red List

　　C．Animals facing extinction

　　D．The IUCN is working to protect fish

　　解析：选A　标题归纳题。本文介绍了太平洋蓝鳍金枪鱼、美洲鳗和中国河豚这三种鱼由于过度捕捞濒临灭绝的情况，故A项标题最贴切。

　　Ⅱ.语法填空

　　When I was young I hated languages. My dad spoke several and was __1__ (ambition) for me. It was not until my graduation from high school __2__ I considered learning a second language - Spanish.

　　I was working in a school for disabled children in a class of six. Only two children could speak, but I realized __3__ (gradual) that every child could communicate. Some of them used physical signs and movements __4__ (express) themselves. Others used their voices - they made noises which changed depending __5__ how they felt. They even "talked" to each other, __6__ (have) arguments and friendly chats like anyone else. Every child in that room had likes and dislikes, desires and fears __7__ they communicated every day, without saying a single sentence.

　　As time went on, I learned not only Spanish __8__ the language of everyone of the children I cared for. I had been making excuses for not trying all these years and here __9__ (be) a group of disabled children showing me __10__

　　important communication really is. It made me want to challenge myself and really learn Spanish.

　　答案：1.ambitious　设空处作表语，意为"有雄心的"，故填ambitious。

　　2．that　设空处所在句为强调句，not ... school为被强调部分，故填that。

　　3．gradually　设空处作状语修饰realized，故填gradually。

　　4．to express　设空处作状语，表目的，且Some of them与express之间是逻辑上的主谓关系，故填to express。

　　5．on/upon　depend on/upon意为"取决于"。

　　6．having　设空处作状语，且They与have之间是逻辑上的主谓关系，故填having。

7．that/which　设空处引导限制性定语从句修饰likes ... fears，且在从句中作宾语，故填that/which。