Answer: The regular verb would be B. developed.
Explanation: A, C, and D are all irregular verbs. A regular verb follows a normal pattern of conjugation. Developed follows this pattern: develop, develops, developed, to develop. The word send does not follow this because the past tense of send is not sended, but sent. The word shoot does not follow this because the past tense of shoot is not shooted, but instead shot. Hang does not follow this because the past tense for this sentence of hang is hung, not hanged. So these verbs are all irregular. Developed is your regular! I hope this helps.
