1 . So far, through the remote video monitoring system and the use of BDS and other equipment, the intelligent and information­based three­dimension system of the “sky and ground” for biodiversity protection ________________ (establish). （所给词的适当形式填空）

2 . Fountain pens ________________ (use) in schools long ago and have been regaining popularity lately because they are refillable. （所给词的适当形式填空）

3 . Investigating the way that dragonflies remain stable during flight actually ________________ (reveal) the techniques they use to get themselves out of tricky situations. (所给词的适当形式填空)

7 . These beautiful black­faced spoonbills are some of the world's rarest birds. The birds ________________ (fly) all the way from their summer home to this wetland, where they will spend the winter. Now, they circle and land. （所给词的适当形式填空）

8 . 生活中总有一些起起伏伏，但是正是苦难让我们更加坚强。
There are always some ups and downs in our lives, ________________. (强调句)