Correct option is A. a true statement that can be proven using facts and cannot be countered
An effective claim in an 'argumentative essay' is a true statement that can be proven using 'facts and cannot be countered'.
EXPLANATION:
An argumentative essay is an essay that consists of two-sided views on a topic. Either both the views are presented in a balanced manner or anyone's view is supported with relevant evidence or finding.
Hence, an effective claim in an argumentative essay will be a true statement that is not hypothetical and can be proved with the help of evidence and facts. Facts can never be denied or encountered. They are not debatable at all. Hence, it can be described as an effective claim.