A researcher selects a sample of n 5 25 high school students and measures the grade point average and the amount of time spent on Facebook for each student. The researcher plans to use a hypothesis test to determine whether there is a significant relationship between the two variables. Which of the following is the correct null hypothesis for the test?

a. r 5 0

b. r ? 0

c. r 5 1.00

d. r ? 1.00