Vaunt - Vaunt means to boast or to praise about something excessively.
Flaunt - Flaunt also means to boast about something or to praise something.
Flaunt is the synonym of the word Vaunt.
Disparate - Disparate means essentially different in its kind or unlike or not able to be compared.
Then the required word is the synonym of Disparate.
Here in the given options, Contrast is the only word which is similar in meaning of Disparate.
Hence, Vaunt : Flaunt :: Disparate : Contrast.