“瘦素”是最近由英国研究人员发现的人体中一种重要激素，它能控制人的食欲。注射“瘦素”后，人的食欲会下降，从而对人体是否发胖起到至关重要的作用。请回答下列问题：

选词填空 选择适当的词并用正确的形式填空，每词限用一次。  

                                                                                    Easy to say and hard to do

    There is ____ old man in a house. In the house there are many mice(老鼠). The old man ____ a cat. Every day the cat catches the mice and eats ____.

    One day, the old mouse says, “All mice must come to my room this evening. We must find a way to do with the cat.”

    All the mice come. Many mice speak, ____ they don't know what ____. At last, a young mouse ____ and says, “We must put a bell(铃铛) on the cat. When the cat comes ____,we can ____ the bell and run away. ____ the cat can't catch us.” “Who can put the bell on the cat?” asks the old mouse. But no one ____.