Four members of a company have a dinner. There are two ladies: A Ling and Xie Li; there are two men: Bo Tong and Li Tang. They are all company employees: sales, accounting, supervisor, liaison. And the supervisor and liaison are husband and wife. They are sitting around a square table: [1] Sitting opposite Po Tong is sales. [2] Sitting opposite Li Tang is not a supervisor. [3] Sitting on the left of A Ling is an accountant. [4] sitting The left of Thanks is not a contact. So, which of the following is the contact? ['Alling.', 'Thanks.', 'Potong.', 'Litang.']