《国家突发公共卫生事件应急预案》根据突发公共卫生事件性质、危害程度、波及范围，将突发

任务型阅读：用括号中所给单词的适当形式填空，补全短文。

       Usagi, also known as Serena, is just a little school girl. She(1)_______(help)a black cat.The cat tums out to be a (2)_____(talk) cat named Luna. Luna gives(3)______ (she) the power(能力)to become a super heroine(女英雄)．Her special power helps  her fight evil(邪恶)and helps her find the "Moon Princess". With a locket Luna gives her, Serena turns into a pretty soldier "Sailor Moon". Then she discovers other Sailor Scouts and ayoung man(4)____(name) Darrien, or Tuxedo Mask. Together they fight the evil forces ofthe Negaverse.

       The (5)_____(story) are very exciting, and all the characters have several names. It was created for Japanese television in 1992 and ran for several years. It has been very popular on TV in America.

我还会写近义词。

连忙——（　　）　突然——（　　）　如果——（　　）　四周——（　　）

如图（a）所示，在光滑水平面上用恒力F拉质量1kg的单匝均匀正方形铜线框，在1位置以速度v₀=2m/s进入匀强磁场时开始计时t=0，此时线框中感应电动势0.8V，在t=3s时刻线框到达2位置开始离开匀强磁场．此过程中v-t图象如图（b）所示，那么恒力F的大小为______ N，线框完全离开磁场的瞬间位置3速度为______ m/s．

什么是光周期现象？在园林花卉生产中有什么意义？