问题：

[单选]

 public class X { 
 public static void main （String[]args）   { 
 string s = new string （“Hello”）； 
 modify（s）； 
 System.out.printIn（s）； 
 } 
 public static void modify （String s）  { 
 s += “world!”；  
   } 
 }     
What is the result？（）  
 

A .  The program runs and prints “Hello”
B .  An error causes compilation to fail.
C .  The program runs and prints “Hello world!”
D .  The program runs but aborts with an exception.