${?}_{{?}_{{?}_{?}}{?}_{{?}_{?}}is\text{a}business\text{p}\text{r}\text{a}\text{c}\text{t}\text{i}\text{c}\text{e}in\text{w}\text{h}\text{i}\text{c}\text{h}\text{a}\text{b}\text{u}\text{y}\text{e}\text{r}\text{s}\text{h}\text{a}\text{p}\text{e}\text{s}\text{a}\text{s}\text{u}\text{p}\text{p}\text{l}\text{i}\text{e}\text{r}s\text{p}\text{r}\text{o}\text{d}\text{u}\text{c}\text{t}\text{s}\text{a}\text{n}\text{d}\text{o}\text{p}\text{e}\text{r}\text{a}\text{t}\text{i}\text{o}\text{n}\text{s}to\text{s}\text{a}\text{t}\text{i}\text{s}\text{f}\text{y}\text{i}\text{t}\text{s}}$

needs.

$[A]$ Reciprocity

$[B]$ Functionalization

$[C]$ Reverse marketing

$[D]$ Bottom$-up$ marketing

$[E]$ Top$-$down marketing