单选题
[填句补文]All children in the United States have to receive an education， but the law does not say they have to be educated at school. A number of parents prefer not to send their children to school. ________. There are about 300，000 home-schoolers in the United States today.
A.Critics also say that most parents are not well qualified to teach their children.
B.In some countries， however， children are educated by their parents.
C.Learning starts with the children's interests and questions.
D.Children who are educated at home are known as “home-schoolers.”
正确答案：D
答案解析：后文出现了home-schoolers，根据选项，这里应该是对这个词的定义，因此选D。