Which is the earliest line in the following code after which the object created on the line marked （0） will be a candidate for being garbage collected， assuming no compiler optimizations are done？ （） 
public class Q76a9 {  
static String f（） {  
String a = "hello"；  
String b = "bye"； // （0） 
 String c = b + "!"； // （1）  
String d = b；  b = a； // （2）  
d = a； // （3）  
return c； // （4）  }  
public static void main（String args[]） { 
 String msg = f（）；  
System.out.println（msg）； // （5） 
 }  
}