题目

Most parents, I suppose, have had the experience of reading a bedtime story to their children. And they must have   1   how difficult it is to write a   2   children's book.  Either the author has aimed too   3, so that the children can't follow what is in his （or more often, her） story,   4   the story seems to be talking to the readers. The best children's books are   5   very difficult nor very simple, and satisfy both the 6    who hears the story and the adult who  7   it. Unfortunately, there are in fact  8  books like this,  9   the problem of finding t已知集合M={1，2，3}，N={2，3，4}，全集I={1，2，3，4，5}，则图中阴影部分表示的集合为（ ）A．{1}B．{2，3}C．{4}D．{5}