Answer:
HS⁻ and OH⁻
Explanation:
Per the Brønsted-Lowry theory, a base is a substance that can accept a proton from another substance
HS⁻ + H₂O ⇌ H₂S + OH⁻
base base
The reaction above is an equilibrium reaction.
In the forward reaction, HS⁻ is acting as a base, because it is "accepting" a proton from water to become H₂S.
In the reverse reaction, OH⁻ is acting as a base, because it is "accepting" a proton from H₂S to become H₂O.
