Attrition Is Particularly Problematic When Obtaining Follow Up Data Because

Attrition is particularly problematic when obtaining follow up data because:

A) loss of too many subjects may alter the reliability of the data
B) low subject response may reflect poorly on the researcher
C) the remaining data may not represent the "true" level of functioning if the complete sample of subjects is not reassessed
D) the amount of time and resources used to re-locate subjects can be extremely costly