Final answer:
The audience for the bulk mail postcard is all of Northern Oregon Energy's customers, as inferred from the reference to 'loyal customers like you' . D option is the correct answer.
Step-by-step explanation:
The audience for the bulk mail postcard is D. All Northern Oregon Energy customers.
This is indicated by the language used in the postcard that references 'loyal customers like you,' suggesting that the postcard is targeted at individuals who are already customers of the energy company.
It also implies that the offer is not available to every Oregon resident or homeowners everywhere since the language is specific to Northern Oregon Energy's customers. Additionally, the message is not exclusively for Bob, as bulk mails are typically sent to a broad audience with similar characteristics or relationships with the company.