Answer: B. the 1101 people interviewed.
Step-by-step explanation:
Given : An opinion poll contacts 1101 adults and asks them, " Which political party do you think has better ideas for leading the country in the 21st century?" In all, 613 of the 1101 say, " The Democrats."
Here, 1101 adults are representing the subset of entire population of adults in US.
Therefore, The sample in this setting is 1101 people interviewed.
Hence, the correct answer is option(B).