根据句意及汉语提示，填入适当单词完成下列句子。 
（1）There are many trees and ____(灌木从)in the garden.
（2）There are some ____ (抢劫者)in the building.
（3）People have different ____(能力).
（4）It's ____  (必要的)to give them clean water if you want them to be healthy.
（5）How ____ (可怕的) the traffic was!

已知整数a₁，a₂，a₃，a₄，…满足下列条件：a₁=0，a₂=-|a₁+1|，a₃=-|a₂+2|，a₄=-|a₃+3|，…，依此类推，则a₂₀₁₂的值为（　　）

战国时期，秦国对六国实施的政治外交策略是（    ）