侧重于分析债务偿付安全性的物质保障程度是（）。 A．资产负债_爱下问搜题

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问题单项选择题

侧重于分析债务偿付安全性的物质保障程度是（）。

A．资产负债率

B．产权比率

C．销售净利率

D．权益净利率

答案

参考答案：A

综合

下图中的格子表示世界人口密度最大的地区，读图后回答下列有关问题：

（1）填出下列数码所示的地区名称：①________________， ②_______________，③__________________。

（2）从地形因素上看，人口稠密区应分布在中低纬度近海的________地区。目前尚无人定居的大洲是___________。

单项选择题

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.

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