One of the key Negative strategies to refute an Affirmative case is to Show that the plan is unfeasible or unsolvable Add more advantages to the Affirmative's plan Refuse to debate the resolution entirely Confuse the judge by introducing excessive evidence

The correct answer is: Show that the plan is unfeasible or unsolvable.<br /><br />In a debate, a Negative strategy to refute an Affirmative case is to demonstrate that the plan proposed by the Affirmative is unfeasible or unsolvable. This means presenting evidence or arguments that show the plan is impractical, impossible to implement, or lacks a viable solution. By doing so, the Negative side can undermine the Affirmative's case and make a strong argument for why the plan should not be adopted.