From the passage, we can learn that the key to improve the education in the U.S. is to____

From the passage, we can learn that the key to improve the education in the U.S. is to______.

A．raise teachers" salary in remote areas

B．provide well-trained teachers for all students

C．rearrange the curriculum so that teachers can have a break

D．allow students to choose their favorite teachers

请帮忙给出正确答案和分析，谢谢！