Definition: You are given a conversation between two people. 'Person1:' and 'Person2:' are used to separate their respective dialogues. You are required to assign a label 'formal' if there is an absence of emotion and a presence of questions anywhere within the conversation. If such pattern is not found assign the label 'informal'.
Input:  Person1:       Well , no one could survive without water , but you see pollution has been making more and more water unable for drinking .  
 Person2:Yeah . Water pollution has for a long time been a major concern among the environmental issues .  
 Person1:        But what are the sources of water pollution ?  
 Person2:They could generally be divided into two categories , direct and indirect contaminant sources .  
 Person1:        Well , direct ones are the pollution directly from factories , refineries waste treatment plants etc . , aren ’ t they ?  
 Person2:Yeah . They are emitted directly into urban water supplies .  
 Person1:        But what about the indirect ones ?  
 Person2:Indirect sources include contaminants that enter the water supply from soils or groundwater systems and from the atmosphere via rainwater .  
 Person1:        I see . For the sake of us all , we should be an active participator in the prevention of it .  
 Person2:Sure . It's an issue asking for everyone's participation . 

formal