阅读理解

People communicate(沟通)in many different ways．The most common way is by talking with others．Besides talking，we can also use body language．When we use body language，we need to use body to show what we mean．Sign language is a kind of body language．Let’s see more about it．

  Sign language is popular among dumb people who are unable to speak or don’t want to speak．If you want to communicate with a foreigner，but you can’t speak his language and he can’t speak Chinese，what can you do?Maybe you can communicate by making signs．Now let’s learn some signs Indians often use．

    *When they are hungry，they move their right hands back and forth in front of their stomachs．

    *When they mean“Let’s eat”．they put their right hands and move them up and down in front of their mouths．

    *When they have had enough，they part their thumbs and first fingers,and move their hands from their chests to chins．

    *If they have a stomachache，they put both hands on their stomachs，and move them back and forth．

已知函数$f\left(x\right)=e^x-mx+1$的图像为曲线C，若曲线C存在与直线$y=\frac{1}{2}x$垂直的切线，则实数m的取值范围是(  )

清朝，康熙帝改变按人口征收丁税的传统做法，宣布推行“固定丁口，永不加税”政策，雍正帝随后把固定的丁税并人土地税统一征收。上述政策（    ）