When Attitude or Opinion Questions Are Asked on a Questionnaire

When attitude or opinion questions are asked on a questionnaire, it has been found that

A) some respondents give opinions on topics about which they know nothing.
B) uninformed responses can be eliminated by adding a "no opinion" choice.
C) most attitudes can be satisfactorily measured with one well-phrased item.
D) open-form attitude items usually provide more valid data.