Suppose that A has obtained a certificate from certification authority X1 and B has obtained certificate authority from CA X2. A can use a chain of certificates to obtain B’s public key. In notation of X.509, this chain is represented in the correct order as –

A. public class Circle implements Shape { private int radius; }B. public abstract class Circle extends Shape { private int radius; }C. public class Circle extends Shape { private int radius; public void draw(); }D. public abstract class Circle implements Shape { private int radius; public void draw(); }E. public class Circle extends Shape { private int radius; public void draw() { /* code here */ } }F. public abstract class Circle implements Shape { private int radius; public void draw() { /* code here */ } }