问题
单项选择题
建立流量试验标准装置的目的是（）。
A.制造厂对非标准化的流量计出厂前逐个进行标定，保证必要的测量精度
B.对已使用的流量计定期校验，以确定其误差是否在允许范围内
C.为了研制新型流量仪表进行中间试验
D.以上都是
答案
参考答案：D
搜题请搜索小程序“爱下问搜题”
建立流量试验标准装置的目的是（）。
A.制造厂对非标准化的流量计出厂前逐个进行标定，保证必要的测量精度
B.对已使用的流量计定期校验，以确定其误差是否在允许范围内
C.为了研制新型流量仪表进行中间试验
D.以上都是
参考答案：D
| 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. |
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