An AI practitioner has trained a model on a training dataset.

Comprehensive and Detailed Explanation:

When a model performs well on training data but poorly on evaluation/test data, it indicates overfitting.

Overfitting: The model memorizes the training data patterns instead of generalizing.

Underfitting (A) means the model performs poorly on both training and test data.

Bias (C) refers to systemic errors in predictions, not this training/test mismatch.

Prompt engineering (B) applies to generative AI, not general ML training models.

???? Reference:

AWS ML Glossary – Overfitting and Underfitting