For the following code, which statement is not true?
a. public class sphere{ private double radius; public double x; private double y; private double z; }the radius, x, y, and z fields are members of the sphere class.
b. the radius field is not available to code written outside the sphere class.
c. the x field is available to code that is written outside the sphere class.
d. the z field is available to code written outside the sphere class.