台風のため、イベントは中止せざるを得なかった。
Q. What does 中止せざるを得なかった convey?
Translation
Because of the typhoon, they had no choice but to cancel the event.
Explanation
〜ざるを得ない means being forced by circumstances to do something reluctantly: 'cannot help but cancel'. It negates the idea of willing choice (A) and clearly states the cancellation happened (C, D).