Answer:
As stated, the students were there in the lab for performing practical without following the safety rules. The most likely basis for teacher's warning here in this case is the flask which is pointed in an unsafe direction. It is not mentioned whether the flask is containing any chemical or not but even if it is empty, it might just fall and break and cause injury to anyone present in the lab because the students are also not wearing proper laboratory wear in accordance to the the safety rules which include lab coats, gloves, eye wear, etc. Also, some students have not tied their hair and more importantly the flasks containing liquids are not labelled. All of these things might end up in a dangerous situation for which the teacher warned students about it all
Explanation:
