Secondary Data Rarely Fit Perfectly the Researcher's Particular Problem

Secondary data rarely fit perfectly the researcher's particular problem.The most important source(s) of lack of fit is(are)

A) out-of-date statistics,differences in units of measurement,differences in class boundaries.
B) differences in units of measurement,theories of measurement,and class boundaries.
C) differences in evaluations of what is important.
D) the volume of data provided is too large.
E) differences in collection method and research design.