You Are Undertaking Research on the Usefulness of 'Coaching' as a Development

You are undertaking research on the usefulness of 'coaching' as a development tool and have found a secondary data set based on a survey undertaken by a Coaching Consultancy of their own clients. You should be wary of deliberate distortion because ________.

A) The data set will be too small to be useful
B) The respondents may have painted the consultancy in an overly favourable light
C) The consultancy may have falsified the results
D) All of these