问题 选择题

读北美洲地形对气候的影响图,完成1—3题。

1、①②③④分别所代表的是[ ]

A、①代表的是冷风

B、②代表的是温和湿润的西风

C、③代表的夏季风

D、④代表的是墨西哥湾暖湿气流

2、③④能够畅行无阻的原因是[ ]

A、西部纵列的高大山脉

B、地势西高东低

C、东部是低矮的平原

D、北美大陆中部平原贯通南北

3、北美的气候类型以:[ ]

A、热带季风气候为主

B、温带大陆气候为主

C、温带季风气候为主

D、温带海洋气候为主

答案

1、D

2、D

3、B

单项选择题
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.

Which of the following does the writer explain

A. Neurotoxins.


B. Microscopic organisms.
C. Predators.


D. Fish walks.