The parties may object to an expert. Therefore, before commissioning an expert to make an opinion, the competent department informs the parties of the expert whom it intends to ask to draw up an opinion and of the subject-matter of the opinion. The communication to the parties states a time limit within which objections to the expert may be made. If the parties do object to an expert, the competent department will decide on the objection.[Rule 121(4); ]