What DataFrame operation outputs a schema of "customer_id LONG, predictions DOUBLE" after importing a model?

The correct answer is based on how the DataFrame operation interfaces with the model and the output schema requirements. The operation, when using the selected syntax, explicitly defines a transformation that utilizes the model's predictions on specified columns while maintaining the necessary structure expected in the output.

By selecting "customer_id" directly from the DataFrame and applying the model to the specified columns, it clearly creates a new DataFrame that directly maps the input column to the output prediction. The aliasing of the predictions as "predictions" immediately indicates what the resulting DataFrame will contain, making the resulting schema straightforward—essentially "customer_id LONG, predictions DOUBLE." This aligns with the characteristics of DataFrame schema creation in a way that fits well with typical data engineering practices, where clarity and structure of data types are vital.

The remaining options either do not present the same structure or clarity in output schema, or they employ different DataFrame transformation methods that may not inherently guarantee the expected schema in the same manner.