Final answer:
The type of sampling technique being used is stratified sampling, which involves dividing the population into different subgroups and selecting a sample from each subgroup.
Step-by-step explanation:
The type of sampling technique being used in this scenario is stratified sampling.Stratified sampling involves dividing the population into different subgroups, or strata, and then selecting a sample from each stratum. In this case, the strata are the different classes (freshmen, sophomore, junior, senior), and 25 students are randomly selected from each class to form the sample.Stratified sampling ensures that each class is represented in the sample, which helps to obtain a more accurate representation of the entire student population.