Which are syntactically valid statement at// point x？（）    
class Person {    
private int a； 
public int change（int m）{
 return m； 
}    
} 
public class Teacher extends Person {    
public int b； 
public static void main（String arg[]）{    
Person p = new Person（）；    
Teacher t = new Teacher（）；   
int i； 
// point x    
}   
} 

A. String s = "Gone with the wind"；String t = " good "；String k = s + t；
B. String s = "Gone with the wind"；String t；t = s[3] + "one"；
C. String s = "Gone with the wind"；String standard = s.toUpperCase（）；
D. String s = "home directory"；String t = s - "directory"；

A. long number = 345L；
B. long number = 0345；
C. long number = 0345L；
D. long number = 0x345L；

A. $persons
B. TwoUsers
C. *point
D. this
E. _endline