问题
选择题
已知点P(-b,2)与点Q(3,2a)关于原点对称点,则a、b的值分别是( ) |
A.-1,3 B.1,-3 C.-1,-3 D. 1,3 |
答案
答案:A
已知点P(-b,2)与点Q(3,2a)关于原点对称点,则a、b的值分别是( ) |
A.-1,3 B.1,-3 C.-1,-3 D. 1,3 |
答案:A
![]() 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 the_小题1:__ 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 _小题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 __小题3:_ each spot on a map. Later, people set off the landmines safely. In the African country of Mozambique, nearly half of the ___小题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. |