Final answer:
The investigator should assume that the fraud investigation report will be challenged in court and should be written with great care.
Step-by-step explanation:
The investigator should choose option a. Assume it will be challenged in court and therefore, should be written with great care. Writing a fraud investigation report with great care ensures that it is accurate, reliable, and can withstand scrutiny in a court of law. By assuming that the report will be challenged, the investigator can anticipate potential challenges and address them in their report.