Fair use refers to the non-commercial use of works published by others without the permission of the copyright owner, and without having to pay remuneration under the circumstances specified in the law. The "cases specified in the law" mainly include: (1) Personal study, research or appreciation, using published works of others; (2) performing published works for free; (3) copying, painting, photography, video recording of artistic works installed or displayed in outdoor public places; (4) Translate published works created in Chinese and written into minority languages and publish works for publication. According to the above provisions, Which of the following are fair use:. ['A sang an unpublished song at the class party.', 'B translates an English work into Mongolian work and publishes it.', 'Company C took the sculptures in the public square and made them into pictures.', 'Ding Wei wrote a paper and copied a paper published by Geng in a journal for reference.']