Answer:
A) mail questionnaires
Step-by-step explanation:
the two main advantages of mailed questionnaires are:
- confidentiality/anonymity: people feel free to respond honestly without having to consider other people's reaction to their responses.
- no interview bias: certain personal issues may generate interviewer bias, and mail questionnaires eliminate that possibility by eliminating the interviewer.
So the answers are generally more honest and that is exactly what Maria is looking for.