Q1:

public Object m() 
{  
    Object o = new Float(3.14F); 
    Object [] oa = new Object[l];
    oa[0] = o; /* Line 5 */
    o = null;  /* Line 6 */
    oa[0] = null; /* Line 7 */
    return o; /* Line 8 */
}

When is the Float object, created in line 3, eligible for garbage collection?

ANS:A - just after line 5

Option A is wrong. This simply copies the object reference into the array. Option B is wrong. The reference o is set to null, but, oa[0] still maintains the reference to the Float object. Option C is correct. The thread of execution will then not have access to the object.