Final answer:
Grace and her fiancé engaged in Mobile commerce by using their smartphones to compare products and prices in physical stores and then purchasing their selections online.
Step-by-step explanation:
Grace and her fiancé's activity of visiting physical stores to gather information about products and then making the purchase online exemplifies Mobile commerce (B). This type of commerce is increasingly prevalent and has been greatly facilitated by advances in technology that allow consumers to compare prices and products on their smartphones before making purchases on the internet from various suppliers at a potentially better price or convenience. With the advent of department stores, shopping became a more standardized experience with fixed prices and the dissemination of mail-order catalogs made an array of products accessible to people even in remote areas. The current marketplace, shaped over time by technology and globalization, now ensures that a consumer can order a variety of goods from anywhere around the world.