D Michelle’s birthstone is a diamond; Debra’s is an opal.
Explanation:
Semicolons serve to link two independent clauses (clauses expressing complete thoughts on their own) with closely related ideas that are not joined by a conjunction such as <em>but, and or, nor, for, yet, </em>or<em> so. </em>
Option D is the correct answer because the clauses Michelle’s birthstone is a diamond; Debra’s is an opal are two independent clauses whose ideas are closely related to each other and that are not joined by a coordinating conjunction.
