The students who were surveyed
All fourth-grade students at the school
All students at the school
All fourth-grade students in the county in which the school is located
Explanation
Correct answer: B.
Choice B is correct. Selecting a sample of a reasonable size at random to use for a survey allows the results from that survey to be applied to the population from which the sample was selected, but not beyond this population. In this case, the population from which the sample was selected is all fourth-grade students at a certain school. Therefore, the results of the survey can be applied to all fourth-grade students at the school.
Why the other choices are wrong
Choice A
Choice A is incorrect. The results of the survey can be applied to the students who were surveyed. However, this isn't the largest group to which the results of the survey can be applied.
Choice C
Choice C is incorrect. Since the sample was selected at random from among the fourth-grade students at a certain school, the results of the survey can't be applied to other students at the school who weren't represented in the survey results. Students in other grades in the school may feel differently about announcements than the fourth-grade students at the school.
Choice D
Choice D is incorrect. Since the sample was selected at random from among the fourth-grade students at a certain school, the results of the survey can't be applied to other fourth-grade students who weren't represented in the survey results. Other fourth-grade students in the county may feel differently about announcements than the fourth-grade students at the school.