Answer
A. More H⁺ and HCO₃⁻ would be produced.
Step-by-step explanation
A solution of carbonic acid, H₂CO3(aq), at equilibrium is represented as shown below:
H₂CO₃(aq) ⇌ H⁺ (aq) + HCO₃⁻(aq)
The addition of more carbonic acid to the solution will shift the system to the right; that is, more H⁺ and HCO₃⁻ would be produced.