Ravi, a new recruit in Solaris Systems, perceives that his outcomes (pay, perks etc.) are lower as compared to his inputs (qualifications, experience...

Ravi, a new recruit in Solaris Systems, perceives that his outcomes (pay, perks etc.) are lower as compared to his inputs (qualifications, experience etc.) in relation to his colleagues. Which of the following theories of motivation explains this phenomenon?

(a)    Need hierarchy theory

(b)    Two-factor model

(c)    Equity theory

(d)    Expectancy theory   

(e)    ERG theory.