单项选择题

Passage One Questions 26 to 28 are based on the passage you’ve just heard.

A.In the US, the public schools are not totally free.
B.Compulsory education in the US includes 9 years of free education.
C.Students mustn’t leave school until they finished grade 12 or reach the age of 16.
D.Books are provided to students free of charge without being returned.