Answer:
The correct answer is:
a) Petroleum jelly
Explanation:
When inserting glass tubing into rubber stopper holes, it's important to take precautions to prevent breakage or damage to the glass and rubber. Lubricating both the stopper hole and the glass tubing can facilitate insertion and reduce the risk of breakage.
Petroleum jelly, also known as Vaseline, is commonly used as a lubricant in laboratory settings because it provides effective lubrication while being inert and non-reactive with most substances. It helps to reduce friction between the glass and rubber, making it easier to twist the glass tubing into the stopper hole without causing damage. Therefore, petroleum jelly is the appropriate lubricant to use in this situation.
