A concurrency self-check tests admission, visibility, atomic transitions, cancellation and completion boundaries.
Review the contracts
Review task admission, cancellation and completion, bounded pending work before answering.
Choose and explain an answer
Ask what event the code actually observes: queued, started, stopped, or completed. Identify the owner of every shared transition.
Select an answer for every question, then check the result and read each explanation. Progress remains in this browser; this is a self-check, not a judged program submission or a credential.
Common Mistakes
A cancelled future does not prove a remote side effect was rolled back. A worker count does not bound an unbounded pending queue.