The parties may put relevant questions to the testifying parties, witnesses and experts including, e.g. in opposition proceedings, witnesses and experts testifying on behalf of other parties. The official in charge of the taking of evidence will determine at what point in the proceedings such questions may be put.

Any doubts on the part of the competent department, e.g. the Opposition Division, or a party as to the admissibility of a question must be settled by the competent department. "Leading questions", i.e. questions which already contain the statement which one would like to hear from the witness, practically only requiring him to answer by "yes" or "no", should be avoided, because they do not allow to properly establish the witness' own recollection of the facts. Questions may further not be directed to facts which require no further discussion, which are in no way relevant to the subject-matter for which the taking of evidence has been ordered, or if they aim at establishing facts in respect of which no evidence has been offered. A decision to reject a question cannot be challenged. As regards the entitlement of other members of the Division to put questions, see III, 8.8.