一Bob，I have trouble      my new telephone．

    一Don't worry．Grandma．I'm show you how to use it.

   

如图所示，两平行金属板AB中间有互相垂直的匀强电场和匀强磁场．A板带正电荷，B板带等量负电荷，电场强度为E；磁场方向垂直纸面向里，磁感应强度为B₁．平行金属板右侧有一挡板M，中间有小孔O′，OO′是平行于两金属板的中心线．挡板右侧有垂直纸面向外的匀强磁场，磁场应强度为B₂．CD为磁场B₂边界上的一绝缘板，它与M板的夹角θ=45°，O′C=a，现有大量质量均为m，含有各种不同电荷量、不同速度的带电粒子（不计重力），自O点沿OO′方向进入电磁场区域，其中有些粒子沿直线OO′方向运动，并进入匀强磁场B₂中，求：

I study in a primary school. ( 改为否定句 )

完形填空

    The lion is one of the most fierce (凶猛的) animals in the world. Lions can be 1 in Africa and India. Lions in Africa can live without water for about one month. Lions are also popular animals in the 2 . Almost every zoo around the world has a few lions.

    It is very 3 for people to tell male and female lions from each other. You can judge (判断) simply by their appearance. A male lion has mane while female lions do not have. Male lion 4 than female lions. A male lion usually weighs about 200 kilograms which is always heavier than a female lion. Both male and female lions have very 5 mouths. They can break the backs of other animals 6. Lions feed on other animals and one lion usually kills between ten and twenty large animals each year for 7 .

    It's unusual for lions to kill people. However, in 1898 two lions 8 and ate over one hundred people in Kenya before they were shot by a British man named P.J. Patterson. This 9 became the subject (主题) of a 1996 Hollywood movie called The Ghost and the Darkness. Now the Indian lions are endangered. It's really necessary for us to 10 the animals, or we won't see them again. Animals are our friends. It is our obligation to protect them.

如图，P（12，a）在反比例函数 $y=\frac{60}{x}$ 图象上，PH⊥x轴于H，则tan∠POH的值为____．