Matilda Is Interested in Number of Books Read by Each

Matilda is interested in number of books read by each of the third grade children in her school district during the academic year. She believes that there may be differences in the number of books read by classroom and by school and she thinks there is a positive relationship between number of books read and reading achievement as measured on the standardized assessment given at the end of the year.
-Matilda's study addresses two primary research questions. One addresses whether there is a positive relationship between number of books read by standardized test score. The type of research addressed by this question represents an) _________research study.

A) Descriptive
B) Casual-Comparative
C) Correlational
D) Experimental