TheTheory of Constraints (ToC), as referenced in PeopleCert DevOps Foundation, states:

A: Every system has at least one limiting factor (constraint) that determines overall performance.

B: System throughput is limited by the capacity of the constraint; improving non-constraints has minimal impact.

C: Focusing improvement efforts on the constraint is the most effective way to improve the performance of the entire system.

In DevOps, constraints may appear in testing, change approvals, environment provisioning, or deployment. By identifying and alleviating these bottlenecks, organizations improve flow and reduce lead time.

Since all three statements (A, B, C) are accurate representations of ToC, the correct answer isD – All of the Above.