The correct answer is "a sensible and valid statement." A sound argument is one that is logically valid and has premises that are both true and relevant to the conclusion. To identify a sound argument, you need to evaluate the logical structure of the reasoning and assess the truth and relevance of the premises. In this case, the other options (a loud remark, an impractical analysis that is hard to prove, and a popular opinion) do not necessarily guarantee a sound argument.
