Read the sentence. when asked about his plan to reduce taxes, the candidate said, “improving the unemployment rate is important.” which logical fallacy is used in the sentence?

The logical connection is absent. The answer lacks any explanation to the question being made. The main problem is that the interviewer is left with a very incomplete response, one that requires a lot of work from part of the interviewer. In this case in particular, even if there were a connection between reducing rates and unemployment, it seems that the candidate does not really have an answer to the question.  That is why the fallacy is the lack of connection or relevance between the question and the answer

the answer is a)   a sentence of death costs the state "almost three times as much as a sentence of life in prison" (delon 147)