Please solve below a. In performing a regression analysis which of the following must be true about the distribution of the error variable? a. The distribution is normal with mean zero. b. The errors associated with one y value are independent of errors associated with another y value. c. The standard deviation is constant for each value of x. Od. All of these choices are true. b. If the standard error of estimate is zero, then: a. the coefficient of determination must be 1.0. b. all the points fall on the regression line. c. there is no unexplained variation left. d. All of these choices are true.