(a) An opinion poll contacts 1787 adults and asks them, " Which political party do you think has better ideas for leading the country in the 21st century?" In all, 691 of the 1787 say, " The Democrats." The sample in this setting is

A. the 691 people who chose the Democrats.
B. all 235 million adults in the United States.
C. the 1787 people interviewed.
D. None of the above.

(b) Archaeologists plan to examine a sample of 4-meter-square plots near an ancient Greek city for artifacts visible in the ground. They choose separate samples of plots from floodplain, coast, foothills, and high hills. What kind of sample is this?

A. A simple random sample.
B. A stratified random sample.
C. A voluntary response sample.
D. None of the above.

(c) A committee on community relations in a college town plans to survey local businesses about the importance of students as customers. From telephone book listings, the committee chooses 183 businesses at random. Of these, 86 return the questionnaire mailed by the committee. The population for this study is

A. the 86 businesses that returned the questionnaire.
B. the 183 businesses chosen.
C. all businesses in the college town.
D. None of the above.