C&D is a local coffee shop that wants to encourage repeat business. What's the most effective way to achieve this?

C&D is a local coffee shop that wants to encourage repeat business. What's the most effective way to achieve this?

Provide coupons on the most frequently purchased donuts.

Provide cash rebates on the most frequently purchased donuts.

Train their staff on the brands of coffee C&D sells.

Thank every customer with a personalized email.

Create a loyalty program for its customers.