At schools fortunate enough to have them, interactive whiteboards are a blessing for educators struggling to engage a generation of students weaned on the Web. In the U. K. —where 70 percent of all primary and secondary classrooms have interactive whiteboards, compared with just 16 percent in the United States - students in those classrooms made the equivalent of five months’ additional progress in math. So far, the data on the efficacy (有效性，功效) of touchscreens in U. S. classrooms is inconclusive, but promising. Multiple recent studies suggest that the devices boost attendance rates and classroom participation. Ever since Dorchester School District 2 in Summerville, S. C. , installed 1,200 interactive boards in its classrooms, disciplinary incidents are way down. "Students were bored" before the touchscreens arrived, says Superintendent Joe Pye. "Trips to the principal’s office are almost nonexistent now. " Which of the following is true according to the passage
A. 16% of the primary and secondary classrooms have installed touchscreens in the U. K. B. 16% of the primary and secondary classrooms have installed touchscreens in the US. C. 16% of the primary and secondary classrooms have installed touchscreens in Dorchester School District 2. D. 70% of the primary and secondary classrooms have installed touchscreens in the US