[QA] The workers only stop the walkout after a new pay offer.

Question:

The workers only stop the walkout after a new pay offer.

• A.
  The worker workers stop the walkout only when a new pay offer.
• B.
  A new pay was offered, which made the walkout stop.
• C.
  Not until a new pay was offered, the workers stop the walkout.
• D.
  Not until a new pay was offered did the workers stop the walkout.