Expert Systems Are Expensive and Time Consuming to Maintain Because

Multiple Choice

Expert systems are expensive and time consuming to maintain because:

A) their rule base is so complex.
B) they rely on equipment that becomes outdated.
C) their rules must be reprogrammed every time there is a change in the environment,which in turn may change the applicable rules.
D) only the person who created the system knows exactly how it works,and may not be available when changes are needed.
E) it is difficult to program at this level of complexity without introducing software bugs.