Among Chen Hua, Liu Gang, and Wang Ming, only one person did homework on Sunday. Chen Hua said, "I do homework at home. " Liu Gang said, "I did not do homework at home. " Wang Ming said, "Chen Hua did not do homework at home. " If only one of these three sentences is true,. So what's the truth ?:. ['Unable to judge.', 'Wang Ming.', 'Liu Gang.', 'Chen Hua.']