What does the phrase "is able" signify about the person's capability?

The phrase "is able" directly relates to an individual's capability or capacity to perform a specific action or task. When someone is described as being "able," it indicates that they have the necessary skills, knowledge, or resources to accomplish something. This suggests a level of competence and readiness that affirms their ability to succeed in a particular area or situation.

In contrast, the other phrases do not convey the same meaning. For example, someone who is "unsure" does not demonstrate confidence in their ability, while "having permission" implies that external approval is necessary rather than inherent ability. The idea of "having attempted" suggests a past effort but does not confirm actual capability. Therefore, "is able" clearly reflects the possession of the ability to perform an action.