The role of an expert is important because:
D. Study and experience bring wisdom which is more valuable than opinion.
An expert is somebody who has a lot of knowledge about a particular subject or topic. An expert will have an educated opinion based on facts and solid arguments. Therefore, an expert plays an important role whenever one needs to make a decision. Although, experts might have contradicting opinions, one can evaluate their arguments and the facts they present, in order to make an educated decision.