${?}_{{?}_{{?}_{?}}{?}_{{?}_{?}}isan\text{e}\text{x}\text{a}\text{m}\text{p}\text{l}\text{e}of\text{a}\text{p}\text{r}\text{o}\text{c}\text{e}\text{s}\text{s}\text{t}\text{h}\text{e}\text{o}\text{r}\text{y}of\text{m}\text{o}\text{t}\text{i}\text{v}\text{a}\text{t}\text{i}\text{o}\text{n}\text{.}}$

$a.$

Hertzberg$s$ two$-$factor motivation theory

$b.$

The acquired needs model

$c.$

The equity theory $of$ motivation

$d.$

Maslow$s$ hierachy $of$ needs