While transforming interrogative sentences into assertive sentences, we add 'not' if the interrogative sentence is in the affirmative and If the interrogative sentence is negative, we remove 'not'.
The process to change Interrogative to Assertive is as follows:
Who+ don’t/doesn’t/didn’t/won't are replaced by Everybody/Everyone +will.
Therefore, the correct transformation is 'Everybody will help a man in distress.'