Sometimes product extensions are created for the purpose of creating a culture or community around a companies brand. Usually "merch" falls in this category. For example, Sidecar Coffee may create a t$-$shirt with their logo on it for the purpose of people identifying with the brand by wearing the t$-$shirt. This type of brand extension is called $\_\_\_\_\_\_\_\_\_\_\_\_\_\_.$

a$.$

Product line extension

b$.$

Complementary brand extension

c$.$

Customer base extension

d$.$

Brand lifestyle extension