It Is the Beginning of the School Year and Ms

It is the beginning of the school year and Ms. Angelo, an eighth grade teacher, is concerned about the students' standardized reading achievement test scores. She knows the current class did not do well the last time that they were tested. She decides to do a study to examine if there are differences in students' gain achievement scores from the last administration based upon the nature of the out of class reading she assigns during the school year. In two of her sections, she allows students to read seven books that they want to read. In two of her other sections, she assigns seven texts. In her last two sections she assigns four texts and allows students to select three.
-What is the dependent measure in Ms. Angelo's study?

A) Type of books read
B) Eighth grade students
C) Gain achievement scores
D) Number of books read