Row access policies (B) are the recommended approach for implementing row-level security in Snowflake, as they are applied at the database level and ensure consistent enforcement regardless of the application accessing the data. Masking policies (D) are crucial for redacting sensitive information based on user roles. Implementing data filtering within the Streamlit application (A) is less secure and harder to maintain. Creating separate applications for each role (C) is inefficient and not scalable. External tables are for accessing data outside of Snowflake not controlling access to existing data.