在JAVA中， 将选项的代码插入下面的位置，编译不会出错的是？(     )

interface IFace {
}
class CFace implements IFace {
}
class Base {
}
public class ObRef extends Base {
    public static void main(String argv[]) {
        ObRef ob = new ObRef();
        Base b = new Base();
        Object o1 = new Object();
        IFace o2 = new CFace();
        // 插入代码
    }
}