"There are fewer close substitutes for the product your team supports" will improve your bargaining position with customers.
Option: B
Explanation:
Bargaining is the procedure which is preferred by citizens not only with street shops but it is famous internationally too, where defense, economic trade deal, etc are signed between two different nations to corporate and shake hand of unity. Bargaining is more effective when one allow seller to know that the party itself have more substitutes if the product is not provided by the seller in appropriate rate.
For an instance, if India need to buy some rolling defense helicopters for nation from Russia but prices are high and United States is providing same material with lower price or may be with better rewards on buying from them.