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问题 单项选择题

关于EPID的描述，错误的是（）

A.EPID的含义是电子射野影像系统

B.EPID系统分为荧光、固体探测器、液体电离室三种类型

C.荧光系统的优点是空间分辨率高，成像速度快，系统视野大

D.固体探测器系统一次可收集射野多个信息，空间分辨率较高

E.EPID的主要功能是验证治疗摆位

答案

参考答案：D

填空题

请在以下程序第一行的下划线处填写适当内容，使程序能正确运行。
______(double,double);
main()
double x,y;
scanf("%1f%1f",&x,&y);
printf("%1f\n",max(x,y));

double max(double a,double B)
return(a＞b a:b);
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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 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
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