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问题 单项选择题

某患者二年前行左肾癌切除术，现B超复查。根据其肝脏超声声像图，诊断为（）

A.肝多发血管瘤

B.肝多发转移癌

C.原发性肝癌

D.结节性肝硬化

E.肝多发性囊肿

答案

参考答案：B

选择题

关于催化剂的说法正确的是（　　）

A．加入催化剂化学反应速率一定加快

B．不使用催化剂就不能发生化学反应

C．使用催化剂能改变物质的化学反应速率

D．使用催化剂可以增加生成物的量
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单项选择题

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.

The word "they" underlined in Paragraph 1 refers to ______.

A. organisms
B. fish

C. toxins

D. flesh
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