下列关于生物实验的叙述，错误的是

如图所示，有一半圆弧光滑轨道，半径为R，在与圆心等高的位置静止放置一个带正电的小球A，其质量为m，MN之间有一方向水平向左的匀强电场，让小球A自由滚下进入匀强电场区域，水平面也是光滑的，下列说法正确的是（   ）

    When you stay away form your home for a long time, you start to miss your good bed, your good parents. Believe it or not, you're feeling homesick. You can help yourself to feel less homesick. Here's how:

      ⑴   .If you're going away from home, bring your favourite clothes, you can also bring some pictures of the people who you may miss. You can look at them any time you want.

       ⑵   .The busier you are, the less time you'll have to feel homesick. Spend your free time on music, sports or books. Try to join in activities whenever you are.

       ⑶   .You can make a plan for when you'll call your mom or dad. You can also keep in touch with family and friends by email or text messages.

       ⑷   .Sometimes, telling someone that you're feeling a little homesick will help you feel better. Maybe you can tell a friend that you feel homesick and the two of you can do something fun.