Answer:
One page
Explanation:
Direct mail questionnaires should be kept to a maximum of a single page.
This is because the target audience of these mails which are the respondents will treat this like they treat regular mails and my not be disposed to answering or giving responses.
So an increased number of pages would surely further decrease the attention the questionnaire would receive from these respondents.
Thus, it is best that the questionnaire is restricted to a single page.
