The best recommendation to reduce the risk of data leakage from employee use of social networking sites for business purposes is to provide education and guidelines to employees on use of social networking sites.
Education and guidelines can help employees understand the benefits and risks of using social media for business purposes, such as enhancing brand awareness, engaging with customers, or sharing industry insights.
They can also inform employees about the dos and don'ts of social media etiquette, such as respecting privacy, protecting intellectual property, avoiding conflicts of interest, or complying with legal obligations.
Education and guidelines can also raise awareness of potential data leakage scenarios, such as phishing attacks, malicious links, fake profiles, or oversharing sensitive information, and provide tips on how to prevent or respond to them.

The most important factor when defining the IS audit scope is to understand the relationship between IT and business risks, as this helps to identify the areas that have the most potential impact on the organization's objectives, performance, and value. By understanding the IT and business risks, the IS auditor can focus the audit scope on the key processes, systems, controls, and issues that need to be assessed and addressed.
References
ISACA CISA Review Manual, 27th Edition, page 256
Ten Factors to Consider when Setting the Scope of an Internal Audit
What Is an Audit Scope? | Auditing Basics | KirkpatrickPrice

The planning phase is the stage of the internal audit process where contact is established with the individuals responsible for the business processes in scope for review. The planning phase involves defining the objectives, scope, and criteria of the audit, as well as identifying the key risks and controls related to the audited area. The planning phase also involves communicating with the auditee to obtain relevant information, documents, and data, as well as to schedule interviews, walkthroughs, and meetings. The planning phase aims to ensure that the audit team has a clear understanding of the audited area and its context, and that the audit plan is aligned with the expectations and needs of the auditee and other stakeholders.
The execution phase is the stage of the internal audit process where the audit team performs the audit procedures according to the audit plan. The execution phase involves testing the design and operating effectiveness of the controls, collecting and analyzing evidence, documenting the audit work and results, and identifying any issues or findings. The execution phase aims to provide sufficient and appropriate evidence to support the audit conclusions and recommendations.
The follow-up phase is the stage of the internal audit process where the audit team monitors and verifies the implementation of the corrective actions agreed upon by the auditee in response to the audit findings. The follow-up phase involves reviewing the evidence provided by the auditee, conducting additional tests or interviews if necessary, and evaluating whether the corrective actions have adequately addressed the root causes of the findings. The follow-up phase aims to ensure that the auditee has taken timely and effective actions to improve its processes and controls.
The selection phase is not a standard stage of the internal audit process, but it may refer to the process of selecting which areas or functions to audit based on a risk assessment or an annual audit plan. The selection phase involves evaluating the inherent and residual risks of each potential auditable area, considering the impact, likelihood, and frequency of those risks, as well as other factors such as regulatory requirements, stakeholder expectations, previous audit results, and available resources. The selection phase aims to prioritize and allocate the audit resources to those areas that present the highest risks or opportunities for improvement.
Therefore, option A is the correct answer.
References:
Stages and phases of internal audit - piranirisk.com
Step-by-Step Internal Audit Checklist | AuditBoard
AuditProcess | The Office of Internal Audit - University of Oregon