A. Since the average test
score (Singular subject) of students enrolled in charter schools were(plural verb) rising 7.5 percent in the spring, many educators concluded ---rejected
B. As the average test score of students enrolled in charter schools rose 7.5 percent in the spring, with many educators
concluding (helping verb missing)
C. Because the average test score of students enrolled in charter schools rose 7.5 percent in the spring, many educators concluded --best candidate, which conveys intended meaning and follows the subject-verb agreement
D. Because the average test
score(Singular subject) of students enrolled in charter schools
were(plural verb) up 7.5 percent in the spring, many educators concluded
E. With average test scores rising by 7.5 percent among students enrolled in charter schools, and many educators concluded (cause-effect relationship is not followed)