Read this statement.

By the year 1870, every state had locally controlled __________.

Which of the following statements best finishes the sentence?

tax-supported schools for elementary-aged school children
normal schools that trained their own teachers locally from within each state
boards of education and superintendents to oversee elementary school teachers
taxes to help pay the salaries of teachers

C?

Yes, the statement is best finished by saying "tax-supported schools for elementary-aged school children.”

To determine the best completion, it's important to understand the context and the phrases used in the sentence. The statement discusses the situation in the year 1870 when something was locally controlled in every state.

To find the answer, we can eliminate the options that do not match the context.

Option B, "normal schools that trained their own teachers locally from within each state," may seem similar, but it does not directly address the idea of schools for elementary-aged children. Normal schools are focused on teacher training, not providing education for children.

Option C, "boards of education and superintendents to oversee elementary school teachers," also does not directly mention the schools themselves. It focuses on the organizational structure and governance of elementary school teachers, rather than the existence of schools.

Option D, "taxes to help pay the salaries of teachers," while partially related, does not capture the entire concept of locally controlled schools. It only mentions the financial aspect of education and does not explicitly refer to the schools themselves.

By the process of elimination, we are left with option A, "tax-supported schools for elementary-aged school children." This option aligns with the original statement and completes it with the most appropriate ending.