In a Survey Using a Split-Ballot Design, Which of the Following

In a survey using a split-ballot design, which of the following is true?

A) Surveys are mailed out in two batches separated by at least one week.
B) Different forms of a survey include some different questions and are administered to selected subjects.
C) Respondents in an interview are given separate forms to be sealed in individual envelopes.
D) Respondents are surveyed twice within a short interval to assess consistency.