给定如下代码:class Circle{String name,radius;int r;public Circle(String n) {name=n;}public Circle(String n,int a) {name=n;r=a;}public Circle(String n,String d,int a) {radius=d;}}要在第三个构造方法的空白处填上一行代码使之能够调用第二个构造方法,这行代码应该是()
A. Circle(n,a);
B. this(Circle(n,a));
C. this(n,a);
D. this(name,a);