龟兔赛了多次,互有输赢。后来龟兔合作,免子把乌龟驮在背上越过了障碍,到了河边,乌龟又把兔子驮在背上游过河去,它们都顺利到达了目的地。龟兔合作的故事给我们的启示是( )
If it had been fine yesterday,we could have watched that air show. But it ________all day.
Yesterday evening,I ________along the street when I suddenly met my maths teacher.
The population of the world ________still ________now.
There ________a basketball match between Class One and Class Three this afternoon.
Our math teacher ________in our school for 20 years and he ________here when he was 23 years old.