在如下源代码文件Test.java中, 哪个是正确的类定义( )
A.
public 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; } }