Test the change in cholesterol level over the two-year period from Exam #2 (Chol2) to Exam (Chol1). Suppose a researcher believes that cholesterol level increases with age. Which of the following is correct, in the hypothesis testing language? (a) The null hypothesis is that the population mean change (Chol2-Choll) is greater than 0, the alternative is that the population mean change is equal to zero. (b) The null hypothesis is that the population mean change (Chol2-Choll) is not equal to O, the alternative is that the population mean change is equal to zero. (c) The null hypothesis is that the population mean change (Chol2-Choll) is not equal to O, the alternative is that the population mean change is greater than zero. (d) The null hypothesis is that the population mean change (Chol2-Choll) is equal to O, the alternative is that the population mean change is greater than zero. (e) The null hypothesis is that the population mean change (Chol2-Choll) is equal to 0, the alternative is that the population mean change is smaller than zero