Machine learning is a branch of computer science that:

Is a tool for developing and executing a wide range of data processing patterns on very large datasets.
Is how you retrieve information from a database.
Is focused on enabling computers to recognize patterns in data—without humans telling the computer how to recognize the patterns.
Is a service to help capture data and rapidly pass massive numbers of messages between other big data tools.

The correct answer is:

Is focused on enabling computers to recognize patterns in data—without humans telling the computer how to recognize the patterns.