If a point lies on the x-axis in a coordinate plane, what must be true? a) the y-coordinate must be negative. b) the y-coordinate must be positive. c) the x-coordinate must be 0. d) the y-coordinate must be 0.

Do one of the following, as appropriate: (a) find the critical value z subscript alpha divided by 2 , (b) find the critical value t subscript alpha divided by 2 . 99%; nequals 17; sigma is unknown; population appears to be normally distributed.