The correct answer is C: 'Implement scheduled scaling to achieve the desired compute level.' This approach is cost-effective and ensures that the necessary EC2 capacity is reached quickly when the batch processing job starts. Scheduled scaling allows you to specify the exact time to scale up and down, ensuring the system is ready by 1 AM and scales down after completion. Increasing the minimum or maximum capacity (options A and B) may not be cost-effective or efficient, and modifying the scaling policy (option D) may not guarantee the desired capacity is met at the specific time required.