D. Not until Bob heard from Jill did he believe she was alright.
Feedback When we invert the sentence with 'not until, not since, only after, only when, only by' we put them in the first place. Be careful and attentive with the word order! The first part after these words is NOT inverted while the second one IS inverted: [not until + subject + verb + object] + [auxiliary + subject + verb + object]