Ndurance, a marketer of exercise equipment uses high prices to sell its high$-$quality devices. Its products are available in a few retail stores in most large cities. Probably less than $10$ percent of all stores that sell exercise equipment are allowed to sell Ndurance branded products. Which degree of market coverage is this?

a$)$ selective

b$)$ intensive

c$)$ pre$-$emptive

d$)$ exclusive