David's IQ Score on the WISC-IV Placed Him in the Low

David's IQ score on the WISC-IV placed him in the low average range of intelligence. One month later, his mother who was very upset, complained to the school that she wants a re-testing because there is no way her could son possibly have an IQ below 120. She suggested that maybe David wasn't feeling well that day or maybe some mistake was made in the scoring, but either way the IQ is wrong. However, the psychologist refused to repeat the test, claiming it would be both a waste of time and a violation of policy. Who is right, and why?

A) The mother, because David should be given the benefit of the doubt. When children don't feel well they tend not to perform at their best. Also psychologists aren't perfect, and while it is unlikely the psychologist made a scoring error, it is possible.
B) The mother. Nobody knows her son better than she, so what she says about her son's intelligence is more valid than a number on a single test.
C) The psychologist. Not only is a person's IQ score highly accurate, it rarely varies by more than a point or two. Therefore, it would be a waste of time to repeat the test.
D) The psychologist. Research has shown that re-administering the WISC IV less than a year later leads to invalidly inflated scores on the second test due to practice effect.