Breaking down user stories into smaller pieces can also impact the acceptance criteria (option B), but the impact on estimation (option C) is typically more significant. Here's a bit more detail:

B. Acceptance criteria: When you break down user stories, you may also need to adjust and define acceptance criteria for each smaller story. Each smaller story will have its own set of criteria that need to be met for it to be considered complete. However, while adjusting acceptance criteria is an important part of breaking down stories, it's often the estimation process that is most significantly affected. Smaller stories make estimation more precise and manageable.

In Agile development, the size and complexity of user stories directly impact the accuracy of estimation, and breaking down larger stories into smaller, well-defined pieces is a common practice to improve estimation accuracy. So, while both options B and C are impacted by breaking down stories, estimation (option C) tends to be the one most affected....