Which is an element of selling hypodermic needles and syringes?

The correct answer highlights that selling hypodermic needles and syringes is typically conducted by individuals who are not classified as professionals in a medical context. The legal framework surrounding the sale of these items often mandates that they be sold only through licensed or professional channels, which can include pharmacies or medical practitioners. The sale by nonprofessionals raises concerns regarding misuse and public health, given the potential for these items to be used in drug abuse or unsafe practices.

In contrast, other options address circumstances or conditions for sales that don't align with established legal parameters surrounding the sale of hypodermic needles and syringes. For example, selling to minors or limited types of buyers does not conform to standard regulations that usually demand a verification of age or licensing. The emphasis on the seller's status as a nonprofessional underscores the importance of regulated transactions in safeguarding public health and preventing illegal drug use or needle sharing.