The correct answer is: A. a, the
The word “boy” is a common noun, which means that it refers to any member of a general class of people or things. In this case, the boy is a member of the class of people who are shy. The word “the” is a definite article, which means that it refers to a specific person or thing. In this case, the grown-ups are speaking to a specific boy, who is the shy boy.
The other options are incorrect because they do not make sense in the context of the sentence. The word “an” is an indefinite article, which means that it refers to a general person or thing. In this case, the grown-ups are speaking to a general boy, who is not the shy boy. The word “no article” is also incorrect because it does not make sense to say that the grown-ups are speaking to no boy.
In conclusion, the correct answer is: A. a, the