The "Total Design Method" for Mail Surveys Recommends Which of the Following

The "Total Design Method" for mail surveys recommends which of the following?

A) TDM recommends that the researcher should help facilitate responses by including a postage paid response device, plus a personalized cover letter.
B) TDM recommends both the careful design of the questionnaire to make it as short as possible and a cover letter expressing the researchers gratitude for the respondents assistance
C) TDM recommends both the careful design of the questionnaire to make is easy to analyse and an accompanying cover letter, saying that for every completed and returned survey a donation will be made to charity
D) TDM recommends both the careful design of the questionnaire to make is easy to complete and an accompanying personalized cover letter emphasizing the importance of the research