单选题 Questions 81-90 are based on the following passage.
It sounds like a science fiction, but researchers say it's a scientific fact: Microscopic organisms dubbed "killer algae" are paralyzing fish with unknown toxins and then eating away at their flesh. They might be making people sick, too.
The name given to this single-cell organism, or dinoflagellate, is Pfiesteria piscimorte- literally, "fish killer. " It was discovered at North Carolina State University in 1988, but at the same time, few scientists believed in its existence, much less in its highly unusual predatory nature. But ongoing research has led to international acknowledgment of the phenomenon and, recently, research funding.
Seemingly prompted by an unknown substance secreted by fish, the aggressive creature swims into action. It sends neurotoxins into the water and air, paralyzing a fish's nervous system, and causing it to gasp for air at the surface. Eventually the fish suffocates. The killer dinoflagellate then attaches itself to the fish and begins sucking away at its flesh. This macabre scenario may help solve several sea mysteries, such as why fishermen report seeing "fish walks" (fish trying to leave the water) and pools of dead fish with holes eaten through them.
Whether humans are affected by the dinoflagellate's toxin remains to be seen. Researchers think it's unlikely eating fresh fish are in danger, but anyone with frequent exposure to the creature could be in peril. Several researchers working with the algae have reported bouts of memory loss and disorientation.
To understand the killer algae further, scientists must fully characterize their toxin and determine what stimulates them to attack. They also need to know if the algae are hurting fish populations, and whether pollutants make them more likely to attack.

单选题 The passage is primarily concerned with ______.
A. informing readers of different sea creatures
B. describing predatory microscopic organisms
C. solving some long-lasting mysteries about the sea
D. discussing the environment for various fishes

【正确答案】 B

【答案解析】[解析] 主旨题型
通读全文可知本文第一段是本文的主旨：讲的是a scientific fact：Microscopic organisms are paralyzing fish with unknown toxins and then eating away at their flesh. They might be making people sick too. 因此整体讲的是Microscopic organisms, B为答案。(第一段讲的是：听上去像一篇科幻小说，但研究人员说这是一个科学事实：一种绰号为“藻类杀手”的微观生物用一种不知名的(生物)毒素麻痹鱼类，然后食用它们的肉。它们也可能会使人类得病。)

单选题 The word "they" underlined in Paragraph 1 refers to ______.
A. organisms B. fish C. toxins D. flesh

单选题 The word "literally" underlined in Paragraph 2 most probably means ______.
A. namely B. superficially C. imaginatively D. actually

【正确答案】 D

【答案解析】[解析] 词义题型
见第二段第一句：The name given to this single-cell organism，or dinoflagellate，is Pfiesteria piscimorte-literally，"fish killer." 可知this single-cell organism即 dinoflagellate，就是Pfiesteria piscimorte，也即“fish killer”；因指的都是一种东西，因此D为答案。

单选题 It is implied in the passage that ______.
A. many scientists had known dinoflagellate before 1988
B. there had been no such organisms before 1988
C. many scientists were in doubt about the nature of the organism in 1988
D. no scientists knew anything about the organism in 1988

【正确答案】 C

【答案解析】[解析] 推断题型
见第二段第二句：It was discovered at North Carolina State University in 1988，but at the same time, few scientists believed in its existence, much less in its highly unusual predatory nature. (1988年在北卡罗莱纳州立大学发现了这种生物，但同时几乎没什么人相信它的存在，更没有人相信它非同寻常的食肉天性(predatory nature)了。)因此C为答案。

单选题 All the following names are used to describe the organism EXCEPT ______.
A. dinoflagellate B. Pfiesteria piscimorte
C. killer algae D. a science fiction

单选题 The word "prompted" underlined in Paragraph 3 means ______.
A. stimulated B. attracted C. annoyed D. shocked

单选题 Which of the following questions is answered according to the information given in the passage?
A. What is the toxin used by the fish killer?
B. Who first discovered the organism?
C. How does the fish killer paralyze fish?
D. How many fishes can the organism kill each day?

【正确答案】 C

【答案解析】[解析] 是非题型
第一段中提到the fish killer有toxins，但没提它使用何种toxins，排除选项A；第二段中提到the fish killer于1988年在大学被发现，但没提及是谁发现的，排除选项B；选项D在文中没有提及；因此C为答案(在第三段第二句中谈到the fish killer向水中、空气中释放神经毒素，麻痹了鱼类的神经系统，使得鱼类钻到水面呼吸；最终鱼类窒息而死；然后它就附着于鱼身食其肉)。

单选题 Researchers think that it is ______.
A. safe to eat fresh fish B. dangerous to get close to the algae
C. safe to be near the algae D. dangerous to expose the algae

单选题 Which of the following does the writer explain?
A. Neurotoxins. B. Microscopic organisms.
C. Predators. D. Fish walks.

单选题 Which of the following statements is true?
A. Scientists have solved the mystery about the fish killer.
B. More studies need to be made about the fish killer.
C. It is proved that the algae are reducing fish populations.
D. Humans have already been affected by the toxin.

【正确答案】 B

【答案解析】[解析] 推断题型
见第五段：To understand the killer algae further, scientists must fully characterize their toxin and determine what stimulates them to attack. They also need to know if the algae are hurting fish populations, and whether pollutants make them more likely to attack. 见下划线部分，因此可知还有更多的研究要做，因此B为答案。