Throughout history, people have thought of the ocean as a diverse and limitless source of food.Yet today there is clear evidence that the ocean has a limit.Most of the big fish in our ocean are now __1__ (go)．One major cause is overfishing.People are taking so many fish from the sea that many species cannot replace __2__ (they)．
For centuries, local fishermen caught only enough fish for their own and their community's needs.However, from the early 20th century, people around the world became interested __3__ consuming proteinrich foods.People began __4__ (catch) large quantities of fish for profit and selling them to worldwide markets.In a very short period of time, commercial fishing __5__ (great) reduced the number of large predatory fish, such as cod and tuna.
Today, there are still plenty of fish in the sea, __6__ they're mostly just the little ones.Small fish, __7__ include sardines and anchovies, have more than doubled in number — largely because there are not enough big fish __8__ (eat) them.
Such large fish __9__ (be) necessary, because they hunt and kill the sick and weak smaller fish.Without this weeding out, or survival of the fittest, ecosystems become less stable.As a result, fish are less able to survive __10__ (difficult) such as pollution, environmental change, or changes in the food supply.
语篇解读：本文是一篇说明文。文章主要介绍了海洋中大鱼数量减少的原因以及由此而造成的后果。
1．gone 考查词性转换。分析句子结构可知，空处作表语，故填形容词gone，意为“不在了，不见了”。注意：此处不表示被动的含义。
2．themselves 考查代词。根据该从句的主语为many species可知，此处应用其反身代词，表示“自我替换”。
3．in 考查介词。be/become interested in意为“对……感兴趣”，为固定用法，故用介词in。
4．catching 考查非谓语动词。begin doing/to do sth.意为“开始做某事”，是固定用法，又由句中的“and selling”可知，此处与selling是并列关系，形式应相同，故填catching。
5．greatly 考查副词。修饰动词一般用副词，故用副词greatly修饰动词reduced，在句中作状语。
6．but 考查连词。根据语境可知，此处表示转折，故用连词but。
7．which 考查定语从句。分析句子结构并根据语境可知，此处引导非限制性定语从句，在从句中作主语，修饰先行词Small fish，故用which。
8．to eat 考查非谓语动词。enough ...to do sth.意为“足够的……去做……”，为固定用法，故用不定式。
9．are 考查主谓一致。根据本句中的they可知， Such large fish表示复数概念，故谓语动词用复数。
10．difficulties 考查词性转换。根据语境中所列举的各种困难可知，此处用名词的复数形式，故用difficulties。
