The Best Rule of Thumb on Follow-Up Mailings in Mail

Multiple Choice

The best rule of thumb on follow-up mailings in mail surveys is that

A) researchers should use as many follow-ups as necessary to achieve a satisfactory response rate.
B) more than one follow-up is ineffective and may anger respondents.
C) more than three follow-up mailings is generally fruitless.
D) a copy of the questionnaire should be included with each follow-up.