I just wonder ____ that makes him so excited.

A．why it does

B．what he does

C．how it is

D．what it is

本题的功能是将文件java2. java复制为文件java2. java. bak。
import java. io. * ;
public class java2
public static void main(String sarg[])
tryFile file=new File("java2. java. bak");
______;
FileInputStream rfile=new FileInputStream("java2. java");
FileOutputStream wfile=new FileOutputStream("java2. java. bak");
int c;
while(______)
wfile. write((char)c);
rfile. close();
wfile. close();
catch(Exception e)System. out. println("读取文件的时候发生错误!");
System. out. println("复制操作完成!");