once you have read the instructions after you have checked your lab equipment after the lab teacher tells you to begin after the lab teacher reads the instructions
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: When can a student safely start an experiment in a science lab?
Possibilities:
- once you have read the instructions
- after you have checked your lab equipment
- after the lab teacher tells you to begin
- after the lab teacher reads the instructions

after the lab teacher tells you to begin