A salt seller used to carry big bags of salt on his donkeys （驴） back to the market every day．
    On the way there， they had to cross a river． One day the donkey suddenly fell into the river． The big bags of salt also fell into the water． Unexpectedly， some of the salt dissolved （溶解） in the water， making the bags much lighter to carry The donkey realized this and felt much more comfortable．
    The next day， the donkey did the same thing on purpose． Again， the bags were lighter and easier to carry．
    The salt seller soon found out what was going on and decided to teach his donkey a lesson．The third day he put two big bags of cotton on the donkeys back． Again the donkey played the same trick，hoping that the bags would become even lighter
    But the cotton that fell into the water became heavier to carry instead． The seller laughed at the donkey and said， "You silly donkey， your trick has been discovered， Don't be too clever， or you would be fooled by yourself．"

（1）Did the seller use to go to the market every day？

Yes，he did．

Yes，he did．

（2）What did the seller put on the donkey's back the third day？

Two big bags of cotton．

Two big bags of cotton．

（3）How many times did the donkey fall into the river on purpose？

Twice．

Twice．

（4）What do you think the donkey will do next time？ Why？

It won't fall into the water．Because the donkey was teased by its owner with a bag full of cotton．

It won't fall into the water．Because the donkey was teased by its owner with a bag full of cotton．