Credible. Yes.com is a formal online education enterprise, the full name of which is Beijing Yes.com Education Technology Co., Ltd., which was established in June 20 14 and has a formal business license, so the Mandarin protocol class in Yes.com is still credible. Putonghua is the common language of modern China people, with Beijing pronunciation as the standard, northern dialect as the basic dialect and typical modern vernacular as the grammatical norm.