Which items are on the bottom layer of the Spark stack?

The bottom layer of the Spark stack typically consists of cluster managers that provide resources and manage the execution of applications across a distributed environment. In this context, YARN (Yet Another Resource Negotiator), Mesos, and Spark Standalone serve as resource managers that facilitate the running of Spark applications by allocating resources like memory and CPU.

YARN is extensively used in big data frameworks and is capable of managing different workloads in a Hadoop environment. Mesos is known for its ability to manage fine-grained resources across different types of applications, including Spark. Spark Standalone is a simple cluster manager provided by Spark itself, enabling users to run Spark applications directly without requiring a separate job scheduler.

This understanding positions option B as the correct choice since it accurately reflects the bottom layer components that provide foundational resource management for Spark. The other options include components that focus on data processing or storage, not specifically on the underlying infrastructure or resource management.