Answer: The students inserting the zippers
Explanation:
The students inserting the zippers are the focus of this study and the reason for the study is to examine the students' sewing skills.
A variable here is the time it takes each student to complete their individual tasks. The independent variables are the number of students, the tools used, and the task, which is the same. The teacher's observation is a quantitative variable as the results are numerical and statistical functions can be applied to them.