person A: I was out walking by the lake over the weekend and there shore was just covered in dead rotting fish.
person B: what happened why were their so many dead fish?
person A: I don't know_comma_ that's what I would like to know! The best I can imagine is that the water quality dropped_comma_ and they died. I imagine it was pollution. 
person B: I hope they are not using the lake for drinking water .