The fact to judge whether the teacher had established rules for the students .
Option b
Explanation:
A teacher has to take care of a whole class with almost 40 students. It is difficult to pay attention to every student personally. When a teacher takes their students for an outdoor activity or to perform any difficult exercise, the teacher needs to explain the activity. It is expected from the student to follow all the instructions of the teacher and listen to all the rules and follow them properly.
If any student gets an injury during the procedure it is necessary to notice whether the injury occurred due to the student's fault. If the student didn't follow the teacher's instructions and deliberately went on with the wrong procedure the judge has to notice that the teacher had established the rules and the student didn't follow teachers' instructions. The teacher hence will not be liable.