Statement II can't be the opening statement as "its effects" refers to something. Therefore, we can say that sentence III is the opening statement. Statement I and IV are spoken by the same person (Dr Nicholson). Therefore, they should be together. The metabolic marker which is mentioned in the statement V is introduced in statement IV. Hence, we can say that IVand V is a mandatory pair. Hence, we can say that option D is the correct answer.