Digital quantities have values that are specified as 1 or 0, HIGH or LOW, etc. The voltage values ...

Digital quantities have values that are specified as 1 or 0, HIGH or LOW, etc. The voltage values associated with these digital quantities fall within specified limits. On the other hand, analog values for physical process control may be any value over a wide range of values, with each different value having a different meaning. As a result:
 
  A) digital computers are unable to monitor or control physical analog operations with any degree of accuracy or certainty.
  B) digital computers are unable to monitor analog physical values regardless of the interfacing techniques used to make the two systems compatible.
  C) digital computers have the capability to monitor only those analog physical operations that fall within the specified ranges of digital HIGH and LOW voltage levels.
  D) digital computers that monitor or control analog physical values must have an accurate means of transforming analog data to meaningful digital data and vice-versa.