(单选题)4: 下列程序的输出结果是
import java.io.*;
public class abc {
public static void main(String args[]) {
String s1="Hello!";
String s2=new String("World!");
System.out.println(s1.concat(s2));
}
}
A: false
B: Hello!
C: Hello!Wofld!
D: 12
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