The correct answer is B – Data preprocessing, which involves cleaning, filtering, and transforming raw data before model training. AWS defines preprocessing as the step where irrelevant or poor-quality data (e.g., excessively short or misrecorded audio) is removed or normalized. The described task—filtering recordings by duration and language—is a textbook example of preprocessing since it prepares the dataset for downstream feature extraction. Feature engineering would occur afterward when converting audio signals into numerical representations (like Mel-frequency coefficients). Model training and data collection come after and before preprocessing respectively. Proper preprocessing ensures data consistency, reduces noise, and improves model accuracy, especially in audio-based healthcare models where clarity and consistency are critical.

Referenced AWS AI/ML Documents and Study Guides:

AWS Machine Learning Specialty Guide – Data Preprocessing and Cleaning

Amazon SageMaker Data Wrangler Documentation – Data Preparation Best Practices