Under Article XVII, Section 4, amendments to or revision of the Constitution shall be valid when ratified by a majority of the votes cast in a plebiscite held:

The correct answer is B. Not earlier than 60 days nor later than 90 days after their approval

Section 4 sets the plebiscite between sixty and ninety days after the approval of the amendment or revision, giving voters time to study the changes. For amendments by people's initiative, the period counts from the certification of the petition's sufficiency.