While They Are Not Fixed and May Rise or Decline

Multiple Choice

While they are not fixed and may rise or decline depending on the circumstances,why do our IQ scores NOT usually increase as we get older

A)  We do not accumulate that much more information as we get older. 
B)  The tests are not designed to measure increases in knowledge as we get older. 
C)  An IQ score is indicative of our relative standing in our particular age group. 
D)  The tests for adults are not comparable to the tests for children.