Consulting refers to an intellectual activity in which people use information as a basis to comprehensively process and create information, intelligence, and materials to provide various services to relevant users in society. Which of the following is a consultation (). ['The teacher asks students questions during class.', 'A student goes to the library in the spare time to ask the staff on duty to retrieve the reference book.', 'Before the start of the China-U. S. Accession negotiations, Chinese personnel asked whether the receivers of the U. S. personnel were intact.', 'In order to judge the case, the judge asked the plaintiff and the defendant about the facts.']