Answer:
Direct mail marketing
Step-by-step explanation:
This is a form of marketing technique in which an organization sends out letters, postcards, samples and other form of promotional materials to target market which may compose of past customers, present customers and potential customers needing the products or services they are offering. Seeing that SparkleClean sends complimentary samples to auto enthusiasts, they are using the direct mail marketing technique. There are a lot of promotional materials that can be used in scenarios like this. Apart from letters and postcards, brochures, catalogs, bulletin and so on can be used.