Answer:
A. All students in Ms. Alvarez's fifth-period class
Explanation:
The options are missing, so I looked them up:
A. All students in Ms. Alvarez's fifth-period class
B. All students in Ms. Alvarez's advisory group
C. Every third student from an alphabetical list of all students in the entire school district
D. Every fifth student from an alphabetical list of all seventh graders in the school
In statistics, the population is the whole number of people (or data) where you can draw a sample from, i.e. the population is the whole group, while the sample represents a smaller number of people that participated in the study or survey.
Options C and D are wrong because a population must include all possible subjects and not just every third student or every fifth one. Option B is also wrong because I doubt that all seventh graders are in her advisory group, since advisory groups tend to be relatively small. The only option left is A and it would be correct if Ms. Alvarez's fifth-period class included only seventh graders (which is more plausible).