As the success of the athletic teams at O$-$MY$-$U skyrocketed, so did attendance at the games. Out$-$of$-$town visitors found all the hotels fully booked. In response, Bob and Shirley opened their home to guests on weekends, operating as a bed and breakfast. Soon many of their neighbors did the same, and Bob and Shirley found they could no longer fill all their rooms every game weekend. How would Michael Porter explain this?

a$.$ The focus strategy was imitated.

b$.$ Demand disappeared.

c$.$ The industry became further segmented.

d$.$ The target segment lost its uniqueness.