$10)$ A large majority of the personal computers $($PCs$)$ in the United States use an operating system purchased from Microsoft. Microsoft's relationship with PC manufacturers is an example of which of Porter's competitive forces? $10)\_\_\_\_\_\_$

A$)$ the bargaining power of buyers

B$)$ competition from substitute goods or services

C$)$ the threat from new entrants

D$)$ the bargaining power of suppliers