Which of the following is good advice about creating research questionnaires for Mark Hammel, research specialist at New Wave Data, to follow?

A. Be concise and clear in the wording of questions.

B. The general context of the survey does not need to be explained.

C. Ask difficult questions in the beginning to "weed out" uninterested respondents.

D. Ask leading questions to encourage specific responses.

E. Use impressive vocabulary to convey the importance of the questionnaire.