以下关于不可抗力的说法，不正确的是( )。
A．不可抗力事件发生在合同生效之后
B．双方订立合同时均不可预见
C．不可抗力事件不能避免且不能克服
D．酒后驾车发生车祸为不可抗力事件
参考答案：D
解析：不可抗力是指当事人在订立合同时不能预见、对其发生和后果不能避免并不能克服的客观情况。不可抗力事件一般包括两大类：一类是自然事件，如水灾、火灾、地震、飓风等，另一类是社会事件，如战争、动乱、暴乱、罢工等。而D项是可以避免的。
| 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