Ping Ping is a doctoral student of business management. She recently completed a study and plans to submit the English version of the paper, which is mainly written by herself, to a foreign management journal. According to the following description, in addition to Ping Ping, who is eligible to become the co-author of the paper? The supervising professor: He inspired Ping Ping's research topic, helped her design the research, and helped her solve problems during the research process. He also reviewed Ping Ping's thesis draft several times and helped her revise the interpretation and deduction of the research results. He was also a sponsor of her research. Professor Williams: He was a professor at an American University who proposed the management theory adopted by Ping Ping in the thesis. He and Ping Ping did not know each other and had no cooperative relationship with one another. However, Ping Ping cited Professor Williams' work several times in her thesis. Professor Wang: He assisted Ping Ping in solving the difficulties related to statistical analysis, discussed the inference of statistical results with her several times, and provided many viewpoints in terms of the interpretation of the research results, most of which were adopted by Ping Ping. Assistant Professor Huang: He allowed Ping Ping to conduct questionnaire surveys with four of his groups. As per the requirements of the research, each group was asked to complete the survey three times, at different stages of the