Final answer:
Topical anesthetics are generally applied for 2-4 minutes, but this can vary based on the product and procedure. It is important to follow specific instructions for the best effect.
Step-by-step explanation:
The duration for which a topical anesthetic should be applied can vary depending on the specific product being used and the procedure that it is being used for. Generally, most topical anesthetics should be applied for approximately 2-4 minutes to ensure that the area becomes numb. However, it is critical to follow the manufacturer's instructions or the advice of a healthcare professional, as some products may require a longer or shorter application time for optimal results. For instance, some dental procedures might use anesthetics that should be applied for a slightly longer period, such as 4-6 minutes, while others might be effective with a shorter application time. If the question is asking which option (a, b, c, d) is correct, and without specifying the type of topical anesthetic or the procedure, 'b. 2-4 min' is a reasonable general guideline.