The most accurate answer is A. Challenge the authenticity of the personal data and have it corrected if needed. This is often referred to as the "right to rectification" and is a fundamental principle of data privacy.  

Here's why:

Accuracy is Key: Individuals have the right to ensure that the personal data held about them is accurate and up-to-date. If data is inaccurate, they should be able to challenge it and have it corrected. This is essential for fairness and preventing harm caused by inaccurate information.  
Why the other options are not always, or universally, true:

B. Set a time-limit as to how long the personal data may be stored by the organization: While data retention limitations are important and often part of regulations (and sometimes, individuals can influence this), data subjects don't generally have the unilateral right to set a specific time limit. Regulations or organizational policies usually dictate retention periods, often based on legal or business requirements.  
C. Obtain a guarantee of prompt notification in instances involving unauthorized access of the data: While many regulations require organizations to notify individuals of data breaches, a guarantee of prompt notification isn't always something the individual can demand. Notification timelines are usually defined by law or regulation.  
D. Evaluate the qualifications of a third-party processor before any data is transferred to that processor: Data subjects don't typically have the right to directly evaluate the qualifications of a third-party processor. However, organizations are responsible for ensuring that any third-party processor they use meets appropriate data protection standards (and often, the data subject should be informed that a third party is used). The data subject's control is more indirect, through regulations and oversight of the primary data controller...