除了口语交流和书面交流，其它的交流形式还有____、____、____、____、____等。

正方形有____个角；有____条边，____边都相等。

阅读下面短文，然后根据括号内所给汉语意思写出单词的正确形式（每空一词）。

    Last weekend I went to visit my grandma. ____ (虽然) her house is far from mine, I still decided to walk there. It was very sunny so I didn't take my ____ (雨伞). However, on the way it began to rain hard. And soon I was all ____(湿的). When I was thinking about what to do next,  ____ (幸运地), there came a taxi. I ____ (停) it and went into it quickly. When I arrived at my grandma's house, she was very surprised to see me.

     "Is it ____ (必要的) for you to come here on foot?  Why didn't you drive your car here?" She asked.

   "Because I want to take more exercise." I answered.

     "Why did you come on ____ (这样的) a rainy day?"

     "I came to tell you a piece of good news."

   "What good news?"

     "I  ____(赢) the first prize in the singing ____ (比赛)."

     "Congratulations!" said my grandma excitedly, then she ____ (给) me a warm blanket to wrap me.

磕头虫是一种不用足跳，但又善于跳高的小甲虫。当它腹朝天、背朝地躺在地面时：将头用力向后仰，拱起体背，在身下形成一个三角形空区，然后猛然收缩体内背纵肌，使重心迅速向下加速，背部猛烈撞击地面，地面反作用力便将其弹向空中（设磕头虫撞击地面和弹起的速率相等）。弹射录像显示，磕头虫拱背后重心向下加速（视为匀加速）的距离约为0.8mm，弹射最大高度约为32 cm。人原地起跳方式是，先屈腿下蹲，然后突然蹬地向上加速。如果加速过程（视为匀加速）人的重心上升高度约为0.5 m，假设人与磕头虫加速阶段加速度大小相等，那么人离地后重心上升的最大高度可达（不计空气阻力的影响）                                      （    ）

在如图所示的电路中,R₁为定值电阻,R₂为可变电阻,E为电源电动势,r为电源内阻.则以下说法中正确的是   （   ）