Final answer:
Spark SQL is the component of the Spark Unified Stack that enables developers to use SQL queries in conjunction with Spark's programming language for advanced data analytics.
Step-by-step explanation:
The component of the Spark Unified Stack that allows developers to intermix structured database queries with Spark's programming language is B. Spark SQL. Spark SQL brings native support for SQL to Spark and streamlines the process of querying data stored in Spark. Not only does it allow for SQL queries to be written and executed on Spark data, but it also allows for mixing these queries with the programmatic data manipulations supported by Spark's RDDs and Data Frames with Scala, Java, Python, or R. Hence, developers can leverage the convenience and familiarity of SQL while benefiting from Spark's advanced analytics capabilities.