The correct option is C A, D
Bronsted acids are proton donors and Bronsted bases are proton acceptors.
For the forward reaction [Al(H2O)6]3+ is the Bronsted acid and HCO−3 is the Bronsted base.
For the reverse reaction, H2CO3 is the Bronsted acid and [Al(H2O)5(OH−)]2+ is the Bronsted base.