单项选择题

class Top { 
static int x = 1; 
public Top(int y) { x *= 3; } 
} 
class Middle extends Top { 
public Middle() { x += 1; } 
public static void main(String [] args) { 
Middle m = new Middle(); 
System.out.println(x); 
} 
} 
结果为:() 

A.1
B.2
C.3
D.编译失败