The correct answer is A because of the fundamental bias-variance tradeoff in machine learning. When model complexity is reduced, the model becomes simpler and less flexible, which decreases variance because it is less sensitive to fluctuations in the training data. However, this simplification comes at the cost of increased bias, meaning the model may oversimplify relationships and fail to capture underlying patterns accurately.
This tradeoff is a core concept in AI fundamentals and directly impacts model performance, reliability, and governance decisions. From an AI governance perspective, understanding this balance is critical when evaluating model risk, as high bias can lead to systematic errors and fairness issues, while high variance can result in instability and unpredictability in outputs. Proper model tuning aims to balance both for optimal and responsible performance.