Answer:
a. the complexity of the product increases.
Step-by-step explanation:
Generally speaking, personal selling often works better than other forms of promotion if the complexity of the product increases.
Personal selling can be defined as a promotional process in which a sales person engages a customer and tries to convince him or her to buy a product. The process involves a face-to-face interaction or communication and as such it is also referred to as the face-to-face selling.
Basically, it is a purchase situation involving a face-to-face interaction between the sales person and the customers, in an attempt to sell a product to them.
Also, note that if the complexity of the product increases, the most effective, efficient and best form of promotion would be personal selling because the sales person will have to explain and demonstrate to the potential customers how to use the product.
Hence, products that are technically complex or have complex features such as mobile phones, office equipments, factory equipment, cars are usually sold using the personal selling method. Any organization or business entity using the personal selling method must ensure their sales personnel have good interpersonal skills, ability, outspoken and very friendly with people.