The word "radical" in the third paragraph is closest in meaning to ______.

A．not very radical for the time
B．used only by the state of Massachusetts
C．enforced by the Massachusetts bar
D．later adopted as a model for the nation's educational system

A．Horace Mann's influence on American education was very great.
B．Horace Mann exerted a small but important influence on American education.
C．Few educators fully understood Horace Mann's influence on American education.
D．The influence on American education by Horace Mann was not appreciate