Final answer:
The sentence fragment is 'Has developed resistance to the drug prescribed by the doctor.' because it lacks a subject, while the other option is a complete sentence.
Step-by-step explanation:
The sentence fragment among the provided options is "Has developed resistance to the drug prescribed by the doctor." This sentence is considered a fragment because it lacks a subject.
A complete sentence requires at least a subject and a verb that together express a complete thought. Meanwhile, Option A, "More than ninety percent of calico cats are female," is a complete sentence because it has a subject, a verb, and expresses a complete thought.
A sentence fragment is a group of words that does not express a complete thought. It is missing a subject or a verb, or it is not an independent clause.
In this case, sentence B, *Has developed resistance to the drug prescribed by the doctor.*, is a sentence fragment because it does not have a subject. It is missing the subject 'It' at the beginning: *It has developed resistance to the drug prescribed by the doctor.*