I know that the answer is A but why In monkeyflowers flower

I know that the answer is A, but why?

In monkeyflowers, flower color is determined in part by a gene \"white\" allele that completely disrupts the function of an enzyme called anthocyanin that otherwise produces a pink pigment. Given the relationship between enzyme activity and pink pigment production shown to the right, what is likely to be the relationship between the pink and white traits in monkeyflowers? A) Pink is completely dominant to white B) Pink is dominant with incomplete penetrance C) Pink is incompletely dominant to white D) White is completely dominant to pink E) None of the above

Solution

ans A pink is completely dominant to white.

The gene that decides the flower colour if disrupts the functional enzyme anthocyanin, the flower colour produced will be white whereas if the enzyme is fully functional (100%) the flower colour expressed is pink.

Here in this graph, 100 percent functional anthocyanin enzyme is present so the white colour allele cannot express itself, so the colour of flower becomes pink as pink is completely dominant over white.