57. What does the expression “IT knowledge reaches its half-life in less than 2 years” imply? (A) It takes 2 years for IT engineers to learn 50 percent of the knowledge they need. (B) Only 50 percent of IT knowledge can be verified to be useful in less than two years. (C) In less than at least two years about most IT knowledge will go through a midterm review. (D) It takes 2 years for 50% of what IT experts know to lose its value, become useless or superseded.