Which of the Following Is Not a Potential Problem for Researcher's

Which of the following is not a potential problem for researcher's using quantitative data from existing secondary sources, such as the US Census or the General Social Survey?

A) The questions used in the existing source might generate open-ended answers that could be incorrectly categorized and coded.
B) The existing source might not ask the specific question the researcher is interested in, making it difficult to interpret and draw conclusions.
C) While the results of quantitative research might show a correlation, it can be difficult to pinpoint a causal relationship and causal factors.
D) Descriptive statistics compiled from these sources may not be sufficiently detailed.
E) All of the above