题干

下列有关质点的说法中正确的是(   )

A:只有质量和体积都极小的物体才能视为质点

B:研究一列火车过铁路桥经历的时间时,可以把火车视为质点

C:研究自行车的运动时,因为车轮在不停地转动,所以在任何情况下都不能把自行车作为质点

D:地球很大,在不停地自转,在研究地球的公转时,可以把它视为质点

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D

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    Ebola is a dangerous virus that can cause people to get very sick and even die. The virus is causing the biggest problems in western Africa, where it has spread quickly.____But it can get worse and cause life-threatening symptoms (症状), such as bleeding and trouble breathing.

____

    Ebola does not spread like colds or the flu because it does not float through the air. Ebola also doesn't spread through food or water, like some other viruses. Instead, Ebola spreads when someone touches the body fluids(液体) of a sick person.

____

    An outbreak is when many people are getting sick with the same illness around the same time. You may have heard of a flu outbreak, which is when lots of people get sick from the same types of flu virus. When an outbreak happens because of a virus, more people could get sick because there is a lot of that virus around.

    Where did Ebola come from?

Scientists aren't sure how the first person gets Ebola at the start. ____ Tropical animals in Africa believed to carry the virus include great apes, chimpanzees, gorillas, monkeys, fruit bats, porcupines, and forest antelopes.

    What do kids need to do about Ebola?

    Ebola is making many people sick in Africa, but no matter where you live, it's always a good idea to wash your hands well and often. ____

A. What is an outbreak?

B. How do people catch Ebola?

C. Why do I need to wash my hands?

D. It's very important that infected people get treatment right away.

E. Ebola symptoms can start with fever and headache, kind of like the flu.

F. But they think that people may pick up the virus by touching or eating infected animals.

G. Keeping hands clean can help protect you from common illnesses like colds and the flu.