—Did the audience participate in the play?
—Yes, the actors ______ to involve the audience were successful.
A. of which the function was
B. whose function it was
把A选项中的 which 改为 whom 这样能对了嘛?
为什么B选项有 it 啊,B选项能去掉it吗,这是 it 作为形式主语的固定句式吗 it is sth (for sb) to do?