In Apache Spark, a Stage is composed of multiple narrow transformations (operations that do not require data shuffling, like map or filter) that can be executed sequentially within the same stage. Stages are separated by wide transformations (e.g., join or groupBy), which require shuffling. A Job corresponds to an action (e.g., collect()) and is divided into stages. Tasks are the smallest units of work within a stage, executed per partition. Slots and Executors relate to resource management, not operation sequencing. Thus, the correct answer is C (Stage).