The river ________ (become) dirty since the paper factory wa

The river ________ (become) dirty since the paper factory wa the river becomes ()because the paper factory pours waste wa The river and air __(pollute)since the paper factory opened That paper factory are pouring d__ water into the river The river has become very dirty和the river has been very dirt He saw a paper factory ——waste water ——the river . A、pouring Factory and c____ make the air dirty It is wrong of them to ________ dirty water into the river o 这道题：The man_____in the factory since 2008. The river became dirty last year.The river has became dirty They have ______ since the factory opened. Three fifths of the water in the river ＿dirty.