一斜面AB长为5m，倾角为30°，一质量为2kg的小物体（大小不计）从斜面顶端A

根据短文内容，用方框中所给的单词的适当形式填空，每词限用一次。

aim   find   fortunate   either   realize

  Most parents, I suppose, have had the experience of reading a bedtime story to their children. And they must 小题1:_______ how difficult it is to write a good children’s book. Either the author has 小题2:_______ too difficult, so that children can’t follow what is in his story, or the story seems to be talking to the readers.
The best children’s books are 小题3:________very difficult nor very simple, and satisfy the child who hears the story and the adult who reads it. 小题4:________, there are in fact few books like this, so the problem of 小题5:________ the right bedtime story is not easy to solve.