Each BRFSS data element (topic) is composed of a series of questions, most of which have a limited number of self-reported, categorical responses. Some questions included within a series may vary by year. The BRFSS questionnaire contains three parts: core sections, optional standard CDC modules and state-specific questions. Fixed core elements (C) are included in the BRFSS questionnaire every year; rotating core elements (RC), questions that are asked every other year; and optional (O) or state-added elements (S), at the state's discretion. Additionally, CDC may add “emerging issue” questions to a fixed or rotating core in any given year. An index by year of topics and the questions contained therein may be obtained from the department.