已定義類ABC：class?ABC{private:??int?x,?y;public:????ABC(int?a,?int?b)??{??x?=?a;??y?=?b;??}};則下列定義對象語句中，錯誤的是？。A.ABC obj;B.ABC *pobj = new ABC(5, 10);C.ABC obj(5, 10);