请看看下面两道Java题,选择哪个答案,并请说明原因!

请看看下面两道Java题,选择哪个答案,并请说明原因!
1．指出正确的表达式().
A． byte = 128;
B． Boolean = null;
C． long l = 0xfffL;
D． double = 0.9239d;
2．指出下列程序运行的结果
public class Example{
String str=new String("good");
char[]ch={'a','b','c'};
public static void main(String args[]){
Example ex=new Example();
ex.change(ex.str,ex.ch);
System.out.print(ex.str+" and ");
System.out.print(ex.ch);
}
public void change(String str,char ch[]){
str="test ok";
ch[0]='g';
}
}
A．good and abc
B．good and gbc
C．test ok and abc
D．test ok and gbc