Answer: technical complexity
Explanation: In simple words, technical complexity refers to the arrangement in which an issue or a task is difficult to do due to its difficult to understand relationship between its internal variables.
Personal selling refers to the process in which an organisation hires some sales personnel who by using their ability and expertise tries to persuade the potential customer to buy the product.
Personal sling is used by the organisations where the product to be sold is technically complex to use as the salesperson can himself or herself educate the customer of how to use the product for maximum benefit.