Because Independent Measures of Achievement,such as SAT Scores,have Not Risen

Because independent measures of achievement,such as SAT scores,have not risen in the past decade,but overall grades in school have risen over the past decade,the most likely explanation for this is

A) student performance in school has changed for the better,and the students are demonstrating more achievement.
B) student performance in school has changed for the better because they are cheating more on tests.
C) instructors have become more lenient,awarding higher grades for the same performance,known as "grade inflation."
D) independent measures of achievement,such as the SAT,are harder tests than they used to be a decade ago.