Enrollments in foreign-language classes at American colleges and universities have jumped 13 percent since 2002, with Arabic and Chinese showing the most dramatic increases, according to a report released on Tuesday by the Modern Language Association. The number of students studying Arabic soared 126.5 percent between 2002 and 2006, while the number studying Chinese grew by more than 50 percent. Korean also rose in popularity, with a 37.1 percent rise in enrollments.