Dúvida questão GC

5. class Rubbish {
 6.   Rubbish r;
 7.   public static void main(String [] args) {
 8.     Rubbish r1 = new Rubbish();
 9.     Rubbish r2 = new Rubbish();
10.     Rubbish r3 = new Rubbish();
11.     r1.r = r2;  r2.r = r3;  r3.r = r1;
12.     r3 = null;
13.     r2 = null;
14.     r1 = null;    
15.     // do stuff
16.   }
17. }

/*
Location:   ... > Section 7: Fundamentals > Objective 7.4 > Question 65
Given:
After which line does the first object become eligible for garbage collection?

A 	after line 11
B 	after line 12
C 	after line 13
D 	after line 14
E 	Compilation fails.

Option D is correct. NOT until line 14 are any objects inaccessible from a live thread.

*/