在下列源代码文件Test.java中,哪个选项是正确的类定义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; } }