Why Did Rathje Resort to Rooting Through Peoples' Garbage Rather

Why did Rathje resort to rooting through peoples' garbage rather than simply asking them questions about their consumption behavior?

A) Because people do not always answer questionnaires accurately and honestly.
B) Because the distribution of households made it impossible to conduct a random sample survey.
C) Because only garbage associated with abandoned houses could legally be examined, and there was therefore no one to ask.
D) Because so many households were included in the study, having people respond to questionnaires would have been an enormous and costly task.