Which Statements Are True, Relative to Systematic Error

Which statements are true, relative to systematic error?

A) If the amount of the systematic error is known, true scores can be retrieved.
B) Systematic error may be decreased by proper instrument calibration.
C) Systematic error results in values that vary in one direction from the true scores.
D) Systematic error results from researcher fatigue or inattention.
E) Systematic error changes the mean but not the relative magnitude of the variance.