Answer:
Stratified sampling
Step-by-step explanation:
In the question, students are selected from subgroups of Sophomore, Junior, and Senior classes.
We are told that 49, 34, and 48 students are selected from the Sophomore, Junior, and Senior classes with 496, 348, and 481 students respectively.
This means that the sample numbers of 49, 34 and 48 students were selected in proportion to the subgroup sizes of 496, 348, and 481 students respectively.
Thus, due to the fact that subgroups were selected & that sample number of students were also selected in proportion to their respective subgroup sizes, this is therefore a stratified sampling.