A. Enable granular locking.

In this scenario, "Lock errors" are most likely caused by contention between the automated processes and manual adjustments to the role hierarchy. Granular locking helps in reducing contention by allowing more parallelism in group membership updates. It will help mitigate these errors by allowing more granular control over the locking mechanism, which reduces the chance of lock contention between the automated and manual tasks.

Since there is a concurrent processing needs, I think the answer is A.

As per documentation:
When the granular locking feature is enabled, the system employs additional logic to allow multiple updates to proceed simultaneously if there is no hierarchical or other relationship between the roles or groups involved in the updates.

https://developer.salesforce.com/docs/atlas.en-us.212.0.draes.meta/draes/draes_tools_granular_locking.htm

From these choices, the answer is possibly C. A is not. This question is awkward. If D were 'defer sharing calculation', the answer could be D.

Seconding Shane, C makes no sense as answer.

Correct answer is A: Enable granular locking.