What is the result?

Given the code fragments:
class Caller implements Callable<String> {
String str;
public Caller (String s) {this.str=s;}
public String call()throws Exception { return str.concat (“Caller”);}
}
class Runner implements Runnable {
String str;
public Runner (String s) {this.str=s;}
public void run () { System.out.println (str.concat (“Runner”));}
}
andpublic static void main (String[] args) InterruptedException, ExecutionException
{
ExecutorService es = Executors.newFixedThreadPool(2);
Future f1 = es.submit (new Caller (“Call”));
Future f2 = es.submit (new Runner (“Run”));
String str1 = (String) f1.get();
String str2 = (String) f2.get(); //line n1
System.out.println(str1+ “:” + str2);
}
What is the result?

A.
The program prints:
Run Runner
Call Caller : null
And the program does not terminate.

B.
The program terminates after printing:
Run Runner
Call Caller : Run

C.
A compilation error occurs at line n1.

D.
An Execution is thrown at run time.