1. Analyze the Context: The sentence describes the scientific process in ancient Greece (protoscientific thought).
- Primary Method: Claims were accepted as true simply "if they were reasonable."
- Secondary Method: Experimental verification was only used "if thought necessary at all."
2. Determine the Required Meaning: Because experimental verification was rarely considered necessary, when it was performed, it was likely done in a superficial, hurried, or routine manner, lacking serious commitment or rigor.
3. Evaluate the Options:
- A. utilitarian: Practical or useful. (Irrelevant to the quality of the verification.)
- B. perfunctory: Carried out with minimum effort or reflection; superficial. (Strong Fit) If verification was hardly necessary, it would be done carelessly.
- C. egregious: Outstandingly bad or shocking. (Too strong; it was indifferent, not necessarily shocking.)
- D. empirical: Based on observation or experience (i.e., experimental). This describes the nature of the verification itself, not the manner in which it was performed, which is what the sentence structure requires.
- E. inductive: Characterized by the inference of general laws from particular instances. (Describes a type of reasoning, irrelevant to the quality of the experimental action.)

The completed sentence reads: In protoscientific (for example, in ancient Greece), claims about the physical world were often accepted as true if they were reasonable; experimental verification, if thought necessary at all, was perfunctory.