完形填空 Scientists in the UK have announced that the piranhafish's reputation 21 a fearsome 22 may well not be deserved. The fish, which is found in the Amazon in Brazil, have been 23 as deadly carnivores (食肉动物) that work in shoals to overwhelm their prey and strip it of its flesh in seconds.
However, experts 24 St Andrews University say that piranhas are omnivores (杂食动物) that mainly eat fish, plants and insects. They form big groups not to hunt but to defend 25 against other predators, according to the team.
'Previously it was thought piranhas shoaled as it 26 them to form a cooperative hunting group,' said Professor Anne Magurran. ' 27 , we have found that it is primarily a defensive behavior.'
Piranhas can be attacked by animals 28 dolphins, caimans and large fish, so forming a shoal is a good way of 29 being killed. Piranhas of 30 age stay in the middle of the group for 31 and the 32 of the shoal differs according to the level of 33 . When the water level is 34 , the fish form small groups as there is space to escape, but when the water level drops, they form large groups as protection 35 predators.

【正确答案】 D

【答案解析】Tell告诉，say说，describe描述，portray描绘。文中have been表明是被动语态，应选择过去分词；根据上下文，这种鱼已被描绘成致命的食肉动物。选项D是正确的。

【正确答案】 B

【答案解析】根据上下文：食人鱼组成巨大的群体并不是为了猎取，而是为了自我保护以抵御其他的捕猎者。因此，这里应选用具有“它们自己”含义的词。选项B是正确的。

【正确答案】 D

【答案解析】Able能够，应与be连用；be able能；enable使能够；enabled是enable的过去式。根据上下文，这里讲的是以前人们对食人鱼的看法，应用过去时。食人鱼的群体活动可以赋予它们合作捕猎的能力。选项D是正确的。

【正确答案】 B

【答案解析】从“我们发现……”一句看出，与以前人们的看法不同，食人鱼的群体活动只是为了保护自己。应选择表示与前句意义相反的转折词。选项B是正确的。

【正确答案】 D

【答案解析】食人鱼群体活动的目的是避免被杀戮(being killed)。Prevent sb. from doing sth. 防止某人做某事，该词通常与from连用，排除选项A和B。of是介词，后跟名词性的词。所以，选项D是正确的。

【正确答案】 B

【答案解析】由此往后连起来看，大意是食人鱼的群体组合是根据所面临的危险，根据水的深浅。并且，处于繁殖期的鱼处于鱼群的中央，以获得保护。Of后应跟名词性词组，age前应有形容词修饰。Reproduce是动词，reproductive是形容词，reproduction是名词，reproductively是副词。选项B是正确的。Reproductive age繁殖期。