Final answer:
The medical office assistant accessing her brother-in-law's medical information without proper authorization would be in violation of the privacy rule set by HIPAA.
Step-by-step explanation:
The correct answer is B. a violation of the Privacy Rule. According to the Health Insurance Portability and Accountability Act (HIPAA), healthcare professionals are required to maintain strict confidentiality of patient records and protect their privacy. The medical office assistant accessing her brother-in-law's medical information without proper authorization would be in violation of this privacy rule.