Where Should Questions About a Respondent's Age, Race, and Gender

Where should questions about a respondent's age, race, and gender be placed in a survey?

A) At the beginning, so the respondents can get comfortable with the survey.
B) In the middle, so the respondents can rest before answering difficult questions.
C) At the end, so the respondents have easy questions to answer when they are tired.
D) It does not matter where these questions are placed.