Trees are planted every year.这句为什么要用被动语态

There are many trees planted There are twenty more trees to be planted.There are _______ _______ trees to be planted. If more trees are planted,our city will be more beautiful.为什么用are 过去式planted There are also 20 trees to be planted什么意思 when are trees often planted by people改为主语动态 More trees——around our city every spring.A.plant B.planted C.are planted D.were planted I planted trees More than 20,000 trees ( ) in 5 years.A will plant B will be plantedC is planted D are planted Many trees ___(plant) in our school yard these years.1.have been planted 2.are planted选哪个?为什么? there are 200 trees( )next yeara.planting b.to plant c.being planted d.to be planted on both sides of the river bank are planted many trees和are many trees planted哪个对?被动语态用于倒状句该怎么办? Lots of trees and flowers______ on both sides of Huangshan Road last yearA、are planted B、were planting C、were planted D、 have planted With lots of trees and flowers________ here and there,our campus looks very beautiful.A. planted B. are planted C. to be planted D. planting -Iigong is becoming more and beautiful. -Yes.Lots of trees and flowers___there years.A.are planted B.will be planted C.have been planted求解析求答案! Look!Some trees _____ by them.A.are planted B.are planting C.have been planting D.are being planD.are being planted They planted one h_____ trees yesterday. There are more than n_____ books in our bookcase. There are lots of trees-----A to plant Bto be planted 理由? More trees are planted to add the b____ of the school