Many trees ________ along the streets every year. So the air is very fresh now.

A．plant

B．are planted

C．planted

D．were planted

目前，（）日益成为警务活动的主要方式，成为克敌制胜的重要战术法宝。

A.各自为阵

B.单兵作战

C.跨地区、多警种联合行动

D.局部活动