A retail company is implementing Einstein Lead Scoring. The data administrator is preparing the dataset for the AI model. The process involves several steps shown in the diagram below. After deployment, the model shows poor performance and seems to be biased against leads from smaller, emerging industries. Which step in the data preparation process is the most likely source of the introduced bias? ```mermaid flowchart TD A[1. Ingest all Lead records from the last 5 years] --> B B[2. Remove Leads with 'Status' = 'Unqualified'] --> C C[3. For Leads with a null 'Annual Revenue' field, fill with the average revenue of all other Leads] --> D D[4. Remove Leads where the 'Industry' field is not in a predefined list of 20 established industries] --> E E[5. Train Einstein Lead Scoring model] ```