Consider the Following Theory: the More One Practices for the SAT

Consider the following theory: the more one practices for the SAT test,the higher the person will score.This theory:

A) is complete and very useful for high school students.
B) is incomplete because it leaves out many other factors that will influence SAT scores.
C) is not useful since it is hard to measure practice time.
D) is useful because more practice will guarantee higher SAT scores.