Final answer:
The best encouragement comes from highlighting the complimentary alteration service, the suit's good appearance on the customer, and the quick service time.
Step-by-step explanation:
The best way for the sales associate to encourage the customer to use the store's alteration services in regard to the business suit with pants that are too long would be option (c): "That suit sure looks nice on you. Are you aware that we offer free hemming on all our slacks? It only takes a couple of days." This response highlights a complimentary alteration service, emphasizes the positive appearance of the suit on the customer, and assures a quick turnaround time for the hemming service, all of which are likely to encourage the customer to make the purchase and use the store's alteration services.