An affinity diagram is a tool used to visually organize and group risks or ideas based on their similarities and categories. It helps in structuring the risks for further analysis and discussion. (Reference: PMBOK Guide, 6th Edition, p. 138)

 According to the PMBOK Guide, an affinity diagram is a tool and technique for the identify risks process that allows large numbers of ideas to be sorted into groups for review and analysis. An affinity diagram can help the risk manager to visually organize the risks identified in the pre-workshop survey by grouping them into categories based on their similarities or common characteristics. This can help the risk manager to facilitate the risk analysis and prioritization in the workshop, as well as to stimulate new patterns of thinking and generate additional risks.

Some of the other options are not relevant or appropriate for the question scenario:

The analytical hierarchy process is a technique for the plan risk management process that provides a method for comparing and ranking alternatives based on multiple criteria. It is not a tool for visually organizing risks.

A SWOT analysis is a technique for the identify risks process that examines the project from the perspective of its strengths, weaknesses, opportunities, and threats. It is not a tool for visually organizing risks, but rather for generating them.

Assigning probability and impact is a technique for the perform qualitative risk analysis process that assesses the likelihood and the potential effect of each individual risk on the project objectives. It is not a tool for visually organizing risks, but rather for evaluating them.

PMBOK Guide, 6th edition, pages 397-399, 414-415, 431-432, 441-442; PMI-RMP Exam Content Outline, 2015, page 7.