Let us reverse the order of the statements
Sentence 1: If a person's conduct does not affect prejudicially the interests of others, it should not come under the jurisdiction of society in the first place.
Sentence 2: As soon as any part of a person's conduct affects prejudicially the interests of others, society has jurisdiction over it, and the question of whether the general welfare will or will not be promoted by interfering with it becomes open to discussion.
Author's intention in the first sentence: If a person's interests are not prejudiced, it should not fall under the jurisdiction of society since there is no benefit for it to be so
Author's intention in the second sentence: If a person's interests are prejudiced, then it falls under the jurisdiction of society but the claim that the latter can improve general welfare is not guaranteed and is opened to discussion
So looking at above two general intentions, the author either:
1) repudiates the utility of society's jurisdiction
or
2) casts doubt on the utility of society's jurisdiction
Hence, we conclude that
D) society's intereference with the actions of individuals does not enhance general welfare
I believe D is best for the above reason