题目

某实验小组为了探究细胞膜的通透性，将小鼠肝细胞在体外培养一段时间后，检测培养液中的氨基酸、葡萄糖和尿素含量（在原培养液中没有尿素），发现它们的含量发生了明显的变化（如图），以下分析合理的是（ ） A. 随培养时间延长，培养液中尿素含量升高，推测其是细胞代谢的产物。B. 随培养时间延长，培养液中葡萄糖和氨基酸含量降低，这肯定是协助扩散的结果C. 培养液中的氨基酸一定是协助扩散进入细胞，其主要作用是合成蛋白质D. 转氨While the presence of rats in homes may cause anxiety and annoyance，they rarely result in driving out the residents.But that is exactly what happened to the inhabitants of the 10-square-mile Hawadax Island off the coast of Alaska，almost 230 years ago.Now thanks to a five-year effort by scientists，the terribly silent “Rat Island” as it had been called for many years has been returned to its rightful owners—birds!Hawadax Island is part of a chain of volcanic islands in the Bering Sea called the Aleutian Islands.The rats that arrived there in 1780，when a Japanese ship carrying them broke down nearby，completely destroyed the native population because the environment of the island was not built to defend its animals from these predators.There isn't any tree on the island，which meant that the birds were accustomed to building their nests low in the ground，giving the rodents(啮齿动物) easy access to both eggs and baby chicks.As years passed，the birds that had called the island home for thousands of years became endangered and eventually，disappeared completely.In 2007，the US FWS(Fish and Wildlife Service) started a serious plan to rid the island of the rats and try bringing back the beautiful birds that had once called it home.Given that there were an estimated 10，000 rodents inhabiting “Rat Island” and the fact that they reproduce rapidly，it was not an easy task.But by 2009，the island was officially declared rat free!Then slowly but surely，the birds began to return. Unfortunately，some of the pioneers were unintentionally killed from the leavings of the raticide，a poison that had been used to wipe out the rodents.But now it seems things are becoming more stable and the island is starting to increasingly look like its former self.Before the transformation，“Hawadax”，also known as “Rat Island”，was a silent and ghostly place with bird bones，snail remains and rocks covered in rat feces(粪便)．Today，birds' singing and flying in and out is a common sight.Tufted puffins and song sparrows，which had long disappeared，are gradually making their way back.Scientists have also been observing an increase in ground nesting and shore birds.Though the island is still not back to its full glory，the signs are encouraging and things can only get better，as time passes.1.The underlined word “that” in Paragraph 1 probably refers to ________.A．birds' being driven outB．the presence of ratsC．birds' returning to the islandD．residents' worrying about rats2.Birds on Hawadax Island became an easy target because ________.A．their chicks were extremely weakB．they nested randomlyC．they reproduced too rapidlyD．this island was treeless3.From the passage，we can know the plan of US FWS ________.A．has helped the island fully recoveredB．cost little but benefited greatlyC．involved poisoning the rats on a large scaleD．accomplished its goal after exactly 24 months4.Which would be the best title for the passage?A．FWS help get rare birds back to alaska islandB．Japanese changed a bird paradise into rat islandC．Alaska's rat island returns to a bird paradiseD．FWS plan to drive rats out of rat Island