is, are, has, have It ____ Jack and Frank who ____ been murdered

is, are, has, have
It ____ Jack and Frank who ____ been murdered.
【正确答案】：is;have
【题目解析】：【考点点击】本题考查强调句型。【要点透析】强调句型结构为“It+is/was+被强调的部分+thatwho”,由此可知,第一个空选择is;主语是 Jack and Frank,因此第二个空谓语动词用复数形式。