Final answer:
The correct answer is 'A. Never;' you should never mix chemicals in a lab setting unless instructed to do so by a teacher, as part of strict safety protocols to prevent accidents and ensure laboratory safety.
Step-by-step explanation:
The correct answer to the question is: A. Never mix chemicals unless or until told to do so by the teacher. In a chemistry laboratory, following strict safety protocols is crucial to prevent accidents and ensure a safe learning environment. Not only should you never taste or touch chemicals, but also you should never mix them without proper authorization or instruction. This precaution is necessary to avoid potentially dangerous reactions that could result in harm or contaminate experiments.
Other lab safety rules to remember include: in case of accidents or chemical spills, report immediately to your teacher; always check with your teacher on how to dispose of chemical waste; and follow instructions carefully when handling flammable chemicals. Additionally, refrain from eating or drinking in the lab, ensure thorough cleaning of all materials, and exercise caution when using heat sources.