In a debate, the second defense is mainly responsible for the following tasks:

1. Rebuttal of the other side's viewpoints: the second defense needs to rebut the other side's viewpoints of the first and second defense. This includes pointing out the logical flaws, factual errors or insufficient evidence of the opponent's viewpoints in order to weaken the opponent's arguments.

2. Consolidate your position: The second defense needs to further consolidate your position based on the refutation of your opponent's viewpoints. This includes emphasizing the strengths of our point of view, providing more evidence and arguments to support our point of view, and explaining why our point of view is more valid.

3. Ask the other side: The second defense also needs to ask the other side questions to reveal the shortcomings of the other side's point of view. These questions can be about the factual basis of the other side's views, logical reasoning, or the reliability of the evidence, so as to provide favorable conditions for the party's subsequent rebuttal and argumentation.

4. Summarize our point of view: In the process of the debate, the second defense needs to summarize our point of view, to ensure that the logic of our argument is clear and well organized. At the same time, the second defense also needs to make a general statement of his side's point of view at the end of his speech, so that the judges and the audience can better understand his side's position.

5. Prepare for the third defense: During the speech, the second defense also needs to prepare for the third defense's speech. This includes anticipating possible rebuttals and challenges from the other side, as well as providing more arguments and evidence to support the third defense.

In short, in the debate, the second defense plays a key role, not only responsible for refuting the other side's viewpoints and consolidating the position of the side, but also to prepare for the subsequent speeches of the side. Therefore, the second defense needs to have strong logical thinking ability, language expression ability and the ability to adapt to the scene.