The main advantages of information technology outsourcing are: (1) outsourcing service providers know more about changing technologies; (2) It can make the most accurate cost forecast, so it can make more accurate budget control; (3) Service providers of professional outsourcing suppliers can provide higher standards and quality services; (4) The company lightens the burden of management professionals, and the enterprise can provide services as needed, without leaving the information technology department in the enterprise for a long time. So the four options A, B, C and D are all correct.