Final answer:
The claim 'It must be an inside job' is a believable opinion because it lacks verifiable evidence and is based on personal belief rather than compelling evidence. The correct answer is B. A believable opinion.
Step-by-step explanation:
The statement 'It must be an inside job' is an example of a believable opinion. It is not presented as a verifiable fact, because it does not provide information that can be confirmed through evidence. It also cannot be categorized as a questionable fact, since it is not claiming to be true based only on questionable evidence or lacking credibility.
Instead, this claim expresses a personal belief or suspicion without presenting compelling evidence that can be verified. In argumentative texts, distinguishing between facts, inferences, and opinions is important, as the strongest arguments are built upon facts that are supported by evidence and inferences reasonably drawn from them.
Focusing on the assertion, if it is made by an authority figure or based on credible evidence, it could potentially shift toward a more factual statement. However, without supporting evidence provided, it remains in the realm of opinion.