How robins（知更鸟） know when it is time                56．＿＿＿＿＿

to go back north？ They seem to tell by how

soon daylight lasts． In late winter， daylight          57． ＿＿＿＿＿

begins to last longest each day． When the               58． ＿＿＿＿＿

daylight lasts long enough， robins start north．        59． ＿＿＿＿＿

They fly by day． Each year they follow a same           60． ＿＿＿＿＿

fly－way． At first， they fly only few miles a          61． ＿＿＿＿＿

day． They stop often in the field to eat bugs           62． ＿＿＿＿＿

（小虫子）． Late， they seem in a hurry． They fly      63． ＿＿＿＿＿

over 100 miles a day． Some are going so far             64．＿＿＿＿＿

as 180 miles． When they get to home， they              65． ＿＿＿＿＿

always stay together high in a tree．
 

参考答案：

56．How后加do             57．soon→long           58．longest→longer   

59．√       60．a→the        61．few前加a         62．field→fields  

63．Late→Later           64．so→as               65．去掉to