根据短文理解，从A、B、C三个选项中选择最佳答案填空。
Ebola (埃博拉) is a river in Africa. In 1976, a 1 virus (病毒) was found there. The virus can cause people to get very sick and even 2. So people call the virus Ebola.
Last year Ebola caused the worst problem in western Africa, and 3 spread very quickly. Medical experts all over the world did their best to stop Ebola and to treat the people who were sick.
Ebola 4 starts with fever and headache, kind of like the flu. But it can get worse and cause serious bleeding and 5 problems. It's very important tor infected (受感染的) people to get treatment right away. People who have Ebola need to be cared for in a special way 6 the illness doesn't spread to doctors, nurses or others in their families.
Doctors aren't sure how the 7 person got Ebola, but they think people picked up the virus from infected animals. People can get the virus by touching an infected person's drops of 8. But Ebola doesn't spread through food or water like some viruses 9. It also doesn't travel through the air like cold or flu viruses do. In areas where the Ebola virus is, anyone who doesn't feel 10 should get medical held immediately.
2NH3该化学反应属于（ ）