【正确答案】：
NO DOUBT SOMEBODY WOULD HAVE NOTICED IF SHE HADN'T BEEN THERE; SHE WAS PART OF THE PERFORMANCE, AFTER ALL.
【题目解析】：考点：毫无疑问：No doubt；注意：notice；一部分：part；演出：performance；毕竟：after all句子结构：本题考查与过去事实相反的虚拟语气。从句：If+主语+had+done；主句：主语+should/would/might/could+have done。