The statement that should be included to establish a claim to back the thesis is option C: "The penalty a polluter must currently pay is in many cases, laughably insignificant." This statement provides evidence to support the argument that polluters should be held accountable for their actions by highlighting the inadequacy of current penalties for polluting. By including this statement, the writer is making a specific claim about the need for stronger consequences for polluters, which supports the overall thesis that polluters should be held accountable for their actions. The other options do not provide specific evidence to support the thesis.