Which sentence is correct?

-The scientist said there is only one thing to be done: to save our river "Stop polluting the groundwater with fertilizers."
-The scientist said there is only one thing to be done to save our river: "Stop polluting the groundwater with fertilizers."
-The scientist said: there is only one thing to be done to save our river "Stop polluting the groundwater with fertilizers."
-The scientist said there is only one thing: to be done to save our river, "Stop polluting the groundwater with fertilizers."

Question

Which sentence is correct? 
 	
-The scientist said there is only one thing to be done: to save our river "Stop polluting the groundwater with fertilizers."
-The scientist said there is only one thing to be done to save our river: "Stop polluting the groundwater with fertilizers."
-The scientist said: there is only one thing to be done to save our river "Stop polluting the groundwater with fertilizers."
-The scientist said there is only one thing: to be done to save our river, "Stop polluting the groundwater with fertilizers."

anonymous · Answer

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