In a solution with the following buffer made of a large amount of carbonic acid and sodium bicarbonate?

Think about the question-

When a large amount of acid is added, what happens to the pH? The pH decreases (1 = very acid, 7 = neutral, and 14 = very basic).

That means the answer can be B or D

When a stress is put on an equilibrium reaction, the reaction shifts to relieve the stress. Adding a large amount of H3O+ to the right side of the reaction equilibrium will cause the equilibrium to shift to the left.

The correct answer is B.

D) pH is falls reaction moves right.'cause high concentration of acids are accumulate in the medium
if strong acid is added in it ,
H2CO3+H2SO4+H2O<=> HCO3- + 4H30+ +SO4-2

As you've noted H2CO3 (weak Carbonic acid) and HCO3- (Bicarbonate ion, conjugate base) is a buffer.

I kind of disagree with the other answers.

Strong acid will dissociate 100% into H3O+ ions and anions

HCl + H2O ====> H3O+ + Cl-

as you can see HCl a strong acid produces H3O+ ions.

This produces excess H3O+ ions that stress the equilibrium reaction that you have provided

The reaction (H2CO3 + ...) would consume the H3O+ according to Le Chatelier's principle which would drive the reaction to the left.

And in fact H2CO3 is then converted to Carbon Dioxide and Water which causes the Medulla's respiratory center to raise the respiratory rate.

So I would say based on my information that the pH would rise and the reaction would move to the left. Because you are decreasing the Hydrogen Concentration

If you could check back so we can know the right answer I'd very much appreciate it.