Explanation
The lead BA should track approvals at the level of individual requirements, as this is the first step to address the root cause of the problem, which is the lack of agreement and clarity on the requirements. By tracking approvals at the level of individual requirements, the lead BA can identify which requirements are causing the most disagreement or confusion, and focus on resolving them with the relevant stakeholders. This can also help to reduce the number of reviews and sign-offs needed, as well as the time and effort spent on them.
Tracking approvals at the level of individual requirements can also provide objective evidence of the progress and quality of the requirements, and support the communication and collaboration among the stakeholders.
The other options are not the best actions to take first. Escalating the problem to the executive management may be necessary at some point, but it is not the first thing to do, as it may create more conflict and pressure, and undermine the lead BA's credibility and authority. Setting limits on duration of sign-offs and the number of reviews may be helpful to manage the expectations and deadlines, but it does not address the underlying issue of the requirements quality and agreement. Offering the stakeholders incentives to sign off documents sooner may be counterproductive, as it may encourage hasty or superficial approvals, and compromise the validity and value of the requirements. References: The answer can be verified from the following sources:
A Guide to the Business Analysis Body of Knowledge (BABOK Guide) Version 3, Chapter 6:
Requirements Life Cycle Management, p. 202-203, 207-208, 211-212.
Business Analysis for Practitioners: A Practice Guide, Chapter 4: Requirements Life Cycle Management, p. 97-98, 101-102, 105-106.