challenge: What was the typical process of interacting with computers before the introduction of the microprocessor in the early 1970s?
  
  A. Users prepared tasks on off-line equipment and processed them in batch mode
  B. Users prepared tasks on off-line equipment and processed them in real-time
  C. Users submitted tasks to the computing center and received output instantly
  D. Users directly interacted with the machine to input tasks
  Answer: 