Which sentence is an example of a linking verb?

The sentence "It was he who bought the tickets" exemplifies a linking verb because "was" serves to connect the subject, "it," with the subject complement, "he." Linking verbs do not express action; instead, they serve to link the subject with more information about that subject. In this case, "was" provides the necessary connection to clarify or identify the subject.

The other sentences primarily feature action verbs. For instance, "ran," "painted," and "sings" all indicate actions undertaken by the subjects. Unlike the linking verb "was," these verbs convey what the subject is actively doing rather than describing a state or condition of being. This distinction is crucial in identifying linking verbs, which often include forms of "to be" and other verbs that express states rather than actions.