学进去

A.mark B. checked C. population D. destroyed E.chemicals

In Tanzania, an African country, a company called APOPO trains African pouched rats(非洲有袋鼠）to find landmines(地雷）left over from the wars. The rats are trained to smell out some of the1．in them. More importantly, these rats are too light to set off the landmines.
Generally speaking, after 8 to 12 months of training, the rats can find landmines so that they can be safely destroyed. Rats and trainers search one small area at a time. To be sure that every inch of the ground is 2．, APOPO workers use a harness-and-rope system that guides the rats back and forth in rows. The trainer stands safely on the edge(边缘) of the area.
When a rat smells landmines, it will dig the dirt in that spot(地点). The trainers 3．each spot on a map. Later, people set off the landmines safely.
In the African country of Mozambique, nearly half of the 4．are younger than 15 years old. A lot of kids are in danger as they play and work. With the help of the rats and trainers, there will be no threat any more.