I think A. Otherwise you would have to wait some time for an answer to be written down.
Since nothing is underlined, I am going to make an educated guess that the underlines clause is "who had worked with the business person". If that is the case, the correct answer would be D - adjective clause. It is a relative clause, to be more precise, because it starts with a relative pronoun "who", but that is a part of adjectival clauses, so that is the correct answer.
For me, this situation depicts the real life situation of every individual. The giant human maze represents life's struggle and problems which is faced by every person in his day to day activities. This can never be taken away from human existence. The challenges will always be a part of everybody's lives.
The reasons why the United States are breaking from Great Britain