What has to occur for a collaborative discussion to be successful? All students offer a different perspective about the same topic.
All group members are able to increase their understanding.
All members ask the exact same number of questions.
All students in the group agree on one idea.

the first one All students offer a different perspective about the same topic.

Explanation:

An instruction method in which learners at various performance levels work together in small groups to complete a task, solve a problem or create a product.

All group members are able to increase their understanding.

Explanation:

It does not matter if all group members have the same idea or perspective or if they all differ. The point of a collaborative discussion is to improve your understanding of that topic, not to simply say "I agree" or "I don't agree".