Which of the following is one of the basic rules of lab work?

The correct choice emphasizes the critical safety practice of avoiding the use of your mouth to pipet hazardous materials. This rule is vital because even if the pipet has been sterilized, there is a significant risk of ingesting toxic substances or pathogens. Using a mouth pipet can lead to serious health hazards, including chemical exposure or infection from biological samples. It is essential to use mechanical pipetting devices or other appropriate methods to ensure safety in the lab environment.

The context of the other options highlights additional safety protocols; however, they do not address this specific and critical rule. For instance, while wearing gloves and labeling samples are crucial practices, they do not protect against the immediate and dangerous risks associated with pipetting hazardous substances orally.