Which of the following is a Bronsted acid but not a Bronsted base?

Bronsted acid – A compound that donates its proton $\left(H^{+}\right)$ to another compound

Bronsted base – A compound that accepts the proton $\left(H^{+}\right)$from another compound

$H_{2}O$ – It is both a Bronsted acid and Bronsted base

$N{H}_3$ – It is both a Bronsted acid and Bronsted base

$H_{2}S$ - It is a Bronsted acid as it donates its proton. It doesn’t accept protons

$HC{O}_3^{-}$ – It is both a Bronsted acid and Bronsted base

Hence, the correct option is (C) $H_{2}S$.