Final answer:
The correct option is 4). The results of tax research may be communicated through a memorandum, a letter, and/or an oral presentation, depending on what is most appropriate for the audience and context.
Step-by-step explanation:
Once tax research has been completed, the researcher may need to communicate the results in a variety of forms, which can include a memorandum, a letter, and/or an oral presentation. These methods of communication are used to present formal reports, findings, and data drawn from research, and can vary based on the audience, purpose, and norms of the field or organization. Formal reports are often complete and highly structured documents that include various sections such as the description of methods, presentation of results (usually with tables or graphs), a discussion or interpretation of those results, conclusions, and recommendations. References and bibliographies are also included to credit sources and support further research. Similarly, memoranda can summarize key findings and provide actionable advice, while letters may communicate results to clients or other stakeholders. Oral presentations can be useful for summarizing and discussing the findings in meetings or conferences.