在下列源代码文件Test. java中，正确定义类的代码是( )。

A．pblic class test
public int x=0;
public test(int x)
this. x=x;

B．public class Test
public int x=0;
public Test(int x)
this. x=x;

C．public class Test extends T1,T2
public int x = 0;
public Test(int x)
this. x = x;

D．protected class Test extends T2
public int x = 0;
public Test(int x)
this. x = x;