It's necessary ____ (reduce) the pollution to the river.
若不等式(3a-2)x+2<3的解集是x<2,那么a必须满足( )
试回答下列问题:
“通过封建契约和分封仪式,如臣服礼、授职礼,领主和附庸形成依附关系。”材料体现的制度是( )