Explanation
Supporting functions are the functions that provide support to the critical functions of an organization, such as human resources, finance, IT, or facilities management. Supporting functions are essential for the continuity of the critical functions, but they are not directly involved in delivering the products or services to the customers.
Supporting functions are also part of the scope of the business continuity management system (BCMS) and need to be identified, analyzed, and protected by the organization. Supporting functions are one of the key concepts of ISO 22301, as they help the organization to determine its business continuity requirements and strategies. References: ISO 22301 Auditing eBook, page 23 1; ISO 22301:2019, clause 8.2.2 2

Explanation
When designing questionnaires for the BIA, the following factors should be considered1:
Concise information: The questionnaires should provide clear and concise information about the purpose, scope, and objectives of the BIA, as well as the instructions on how to complete them. The questionnaires should also avoid unnecessary or redundant questions that could confuse or frustrate the respondents.
Layout: The questionnaires should have a logical and consistent layout that facilitates the readability and comprehension of the questions. The questionnaires should use appropriate fonts, colors, spacing, and numbering to highlight the key points and sections. The questionnaires should also use tables, charts, or graphs to present the data or information in a structured and visual way.
Types of question: The questionnaires should use different types of questions to elicit the required information from the respondents. The questionnaires should use open-ended questions to allow the respondents to provide their own opinions or explanations, closed-ended questions to obtain specific or quantitative data, and rating or ranking questions to measure the relative importance or priority of the factors or criteria.
Level of detail: The questionnaires should provide the appropriate level of detail for the BIA. The questionnaires should not be too general or vague, as this could lead to inaccurate or incomplete results.
The questionnaires should not be too specific or technical, as this could overwhelm or intimidate the respondents. The questionnaires should balance the depth and breadth of the information needed for the BIA.
References: 1: ISO 22301 Auditing eBook, Chapter 5: Business Impact Analysis and Risk Assessment, Section 5.2: Business Impact Analysis, Subsection 5.2.3: Data Collection Methods, Page 69.