I think the answer is d...
C. His hours are long and busy.
Linking verbs are do not express action. It simply links the subject of the verb to the additional information about the subject.
In the above sentence, ARE is the linking verb. It does not express any action. Its subject is his hours. It connects the additional information long and busy to the subject his hours.
Verbs in other choices pays, works, and has walked are all action verbs. It does not connect the subject to additional information about the subject. Instead, the verb shows the subject doing the action (he works, he has walked) or the subject receiving the action (his boss pays him).
The first statement corresponds to a Statement of reason. The linker "because" indicates reason, so what follows is a the reason why extreme celebrity workship is a serious problem.
The second thesis statement corresponds to a cause and effect structure. This is best indicated by the verb "caused by" which introduces the causes that lead to Extreme celebrity workship, which would be the effect.
The last thesis statement corresponds to the structure problem and solution. The word 'solved' is a good indication of the structure. As a result, what follows is a solution to the problem of Extreme celebrity solution.