According to the lecture, what is the primary factor that distinguishes between $B2C$ and $B2B$ products$/$services$?$

a$.$ price

b$.$ There is no difference between B$2$B and B$2$C products$/$services$.$

c$.$ whether the product$/$service is available for purchase online $($B$2$B products$/$services aren't sold online, while B$2$C products$/$services are.$)$

d$.$ intended use