For the following code, which statement is not true?

```
public class Sphere
{
private double radius;
public double x;
private double y;
private double z;
}
```

a. The z field is available to code written outside the Sphere class.
b. The radius field is not available to code written outside the Sphere class.
c. The radius, x, y, and z fields are members of the Sphere class.
d. The x field is available to code that is written outside the Sphere class.

a. The z field is available to code written outside the Sphere class.