Answer:
D. Population, because it is a collection of salaries for all teachers in the school.
Step-by-step explanation:
In research, population refers to a complete set of subjects that share a characteristic and that the researcher is interested in. On the other hand, a sample is a subset of a population and it's usually the one the researcher takes to make a study with.
In this example, we have "The salary of each teacher in a school" since we are taking ALL the teachers of this school, this would be a population. If we were working with the salary of only a portion of the teachers of said school, it would be a sample.
Thus, the right answer is D. Population, because it is a collection of salaries for all teachers in the school.