Color Plate shows how the color of the acid-base indicator bromocresol green (H2BG) changes as NaCl is added to an aqueous solution of (H+)(HBG2-). Explain why the color changes from pale green to pale blue as NaCl is added.

in chemistry, a solution’s concentration is how much of a dissolvable substance, known as a solute, is mixed with another substance, called the solvent. the standard formula is c = m/v, where c is the concentration, m is the mass of the solute dissolved, and v is the total volume

i think it's letter a.