Passage Two
When we think of animals and plants, we have a pretty good way of dividing them into two distinct groups: one converts sunlight into energy and the other has to eat food to make its energy.
Well, those dividing lines come crashing down with the discovery of a sea slug (海蛞蝓) that's truly half animal and half plant. It's pretty incredible how it has managed to hijack the genes of the algae (藻类) on which it feeds.
The slugs can manufacture chlorophyll, the green pigment (色素) in plants that captures energy from sunlight, and hold these genes within their body. The term kleptoplasty is used to describe the practice of using hijacked genes to create nutrients from sunlight. And so far, this green sea slug is the only known animal that can be truly considered solar-powered, although some animals do exhibit some plant-like behaviors. Many scientists have studied the green sea slugs to confirm that they are actually able to create energy from sunlight.
In fact, the slugs use the genetic material so well that they pass it on to their future generations. Their babies retain the ability to produce their own chlorophyll, though they can't generate energy from sunlight until they've eaten enough algae to steal the necessary genes, which they can't yet produce on their own.
“There's no way on earth that genes from an alga should work inside an animal cell,” says Sidney Pierce from the University of South Florida. “And yet here, they do. They allow the animal to rely on sunshine for its nutrition. So if something happens to their food source, they have a way of not starving to death until they find more algae to eat.”
The sea slugs are so good at gathering energy from the sun that they can live up to nine months without having to eat any food. They get all their nutritional needs met by the genes that they've hijacked from the algae.
What is the distinctive feature of a sea slug?
第一段第二句指出，然而，在发现海蛞蝓的时候，这些分界线变得模糊不清了，海蛞蝓确实属 于一半动物一半植物，这句话中的 “这些分界线”是指上一句提到的，动物靠进食来获取能量，植物靠光合作用从阳光中获取能量。也就是说，海蛞蝓兼具动物和植物的特性，即它既能从食物中又能从阳光中获取能量。最后一段也指出，海蛞蝓的基因让它们可以靠阳光来产生营养物质，所以，如果它们的食物来源出了问题，它们在找到更多的海藻来吃之前有办法不被饿死。由此可知，本题应选D。 选项A是对原文 half animal and half plant的误解，并不是说它长得既像动物又像植物，故排除。选项B和C的内容都与原文不符，均可以排除。
What enables the sea slug to live like a plant?
第一段最后一句指出，关于它是如何成功地劫持了它赖以为食的藻类的基因，实在是一件令人 不可思议的事，然后第二段进一步解释了它是如何劫持藻类的基因的，第二段第二句指出，盗食质体这个专有名词就用来描述使用劫持来的基因借助阳光创造营养物质的做法。由此可知，海蛞蝓之所以可以像植物一样生存是因为它从海藻那里窃取的基因让它能够进行光合作用，故本题选A。 the genes it captures from the sea plant algae 同义替换原文中的hijack the genes of the algae。选项B 、C和D的内容都与原文不符，均可以排除。
What does the author say about baby sea slugs?
第三段第二句指出，虽然刚出生的海蛄蝓在吃掉足够多的海藻以窃取必要的基因（这类基因是它们自己还不能创造的）之前无法利用阳光产生能量，但是它们保持了可以自己制造叶绿素的能力。由此可知，刚出生的海始蝓可以自己产生叶绿素，故本题选D 。选项A 和B 的内容原文没有提及，可以排 除，选项C是最后一段讲海始蝓的内容，不是讲baby sea slugs ,故也可以排除。
What does Sidney Pierce say about genes from an alga?
第四段第一句指出，南佛罗里达大学的西德尼•皮尔斯称：“海藻的基因绝对不可能在动物细胞里起作用，然而在海蛞蝓的身上，这种情况发生了。”也就是说，西德尼•皮尔斯认为一般情况下海藻的基因不太可能在动物的细胞里起作用，故本题选C。 function inside animal cells同义替换原文中的work inside an animal cell。选项A、 B和D的内容原文都没有提及，均可排除。
What do we learn about sea slugs from the passage?
文章最后一段指出，海蛄蝓特别擅长从太阳那里聚集能量，它们可以在不吃任何食物的情况下活九个月，这与选项B 的内容一致，故本题选B。survive for months without eating与原文live up to nine months without having to eat any food是同义替换。选项A、C和D 的内容原文没有提到，均可排除。