Answer: (iv) Data Encryption

Standard data preprocessing steps in data mining are:

1. Data Cleaning — handle missing values, noise, outliers, inconsistencies.
2. Data Integration — merge data from multiple sources into a coherent store.
3. Data Reduction — reduce volume (dimensionality/numerosity reduction) while preserving analytical value.
4. Data Transformation/Discretization — normalize, aggregate, or bucket data into a mining-ready form.

Data Encryption is a security measure (protecting data confidentiality), not a data-quality or mining-readiness step — it has no role in the standard preprocessing pipeline, making it the correct "NOT a step" answer.